JP3387291B2 - Semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bipolar normally-off vertical power device.

[0002]

2. Description of the Related Art As a prior art, Japanese Patent Laid-Open Publication No. 6-2
The semiconductor device disclosed in No. 52408 will be introduced. Figure 7
10 is quoted from the above publication. 7 is a perspective view for explaining the basic structure of the device, FIG. 8 is a cross-sectional view showing the same portion as the front face of FIG. 7, FIG. 9 is a plan view of the device, and FIG. 10 is the same cross-sectional view as the side face of FIG. FIG. 8 is a sectional view taken along line AA ′ in the plan view of FIG. 9 perpendicularly to the paper surface, and FIG. 10 is a sectional view taken along line BB ′ similarly.
It has a relationship of hitting. Note that, in FIGS. 7 and 9, for the sake of explanation, a state in which the metal film which is the electrode on the surface and the surface protective film are removed is drawn.

First, the device structure will be described. This conventional example is filed by the applicant of the present invention, and the names of each part will be appropriately changed and described within the range not departing from the contents of the above publication. In the above figure, 1 is an n ⁺ type substrate region,
2 is an n-type drain region, 3 is an n ⁺ -type source region, 4
Is a MOS type electrode, and 5 is an insulating film. The MOS type electrode 4 is made of high concentration p ⁺ type polysilicon. A drain electrode 11 is in ohmic contact with the substrate region 1.
A source electrode 13 is in ohmic contact with the source region 3 and the MOS electrode 4. That is, the MOS electrode 4 is fixed at the source potential. Therefore this MOS
Formed electrode 4 and insulating film 5 are combined to form "fixed potential insulating electrode" 6
Call. As shown in FIG. 8, the sectional structure of the fixed potential insulating electrode 6 is formed in a groove whose side wall is substantially vertical like a letter "U".

Further, the portion of the drain region 2 sandwiched between the fixed potential insulating electrodes 6 in FIG. 8 is called a channel region 7. In this state, a depletion region is formed in the drain region 2 around the fixed potential insulating electrode 6 from the MOS type electrode 4 due to the electric field due to the work function difference. A potential barrier is formed in the channel region 7 by the depletion region for conduction electrons that form the main current, and the source region 3 and the drain region 2 are in a cutoff state as they are. Since the structure of the channel region forms this potential barrier, it is desirable to make the channel thickness H as narrow as possible. As an example, the channel thickness H is about 2 μm. Further, the channel length L shown in FIG. 8 is set to 2 to 3 times or more the channel thickness H so that the channel does not punch through even if the drain electric field is increased.

Further, a p-type injector region 8 exists in a position in contact with the insulating film 5 and away from the source region 3. In FIG. 10, reference numeral 18 denotes an electrode which makes ohmic contact with the injector region 8 and is called an "injection electrode". Further, 9 is an interlayer insulating film, and the broken line in the figure shows the existence of the fixed potential insulating electrode 6 in the depth direction of the paper surface, as can be seen from the relationship with FIG.

Next, the operation will be described. In this element, for example, the source electrode 13 is grounded (at 0 V) and the drain electrode 1
1 is used by applying an appropriate positive potential via a load. First, when the injection electrode 18 is grounded, the device is in the cutoff state. Further, in this state, a depletion layer extends in the drain region 2 due to the drain potential. Among a small amount of carriers generated in the depletion layer, conduction electrons flow away to the drain electrode 11 through the n ⁺ type substrate region 1, and holes reach the interface of the insulating film 5 on the surface. However, when the potential at the interface of the insulating film rises due to this, the holes move to the p-type injector region 8 having a low potential in contact therewith, and flow away through the injection electrode 18. Therefore, holes do not stagnate in the channel region, and the element keeps the cutoff state.

Next, although it is turned on, the potential of the injection electrode 18, that is, the potential of the p-type injector region 8 is, for example, +
When 0.5 V is applied, holes flow from the p-type injector region 8 to the interface of the insulating film 5 in contact therewith, contrary to the above, and raise the potential of the interface. Then, the holes block lines of electric force from the MOS electrode 4 to the channel region 7 and lower the potential barrier in the channel region 7. That is, this brings the drain region 2 and the source region 3 into conduction. When the potential of the injection electrode 18 is further increased, the pn junction composed of the p-type injector region 8 and the peripheral n-type region is forward biased, and holes are directly injected into the drain region 2 and the channel region 7. Then, in order to maintain the breakdown voltage, the impurity concentration is made thin, and the conductivity of these n-type regions, which have been made to have high resistance, is increased, and the current flows with low resistance. In this way, the channel region 7
Is used as a hole conduction path, the fixed potential insulating electrode 6 is formed in a stripe shape as shown in FIGS.

Once the current flows in this way, this element can be regarded as a current control type element. A current-voltage curve with a constant injection current has the same shape as that of a vertical bipolar transistor as shown in FIG. 11, for example. That is, when the drain potential is low, the current curve shows a steep slope almost in proportion to the drain potential (linear region), but when the drain potential becomes high, the slope of the current curve becomes extremely dull (pseudo saturation region). ),
Further, the current value is almost saturated where the drain potential is high.

When this element is used as a switching device having a high current capacity, the operating point is as shown by point A in FIG. . When operated in the state of point C, a larger current can flow, but the power loss in the element becomes several times. By the way, FIG. 12 is a graph schematically explaining the density distribution of holes in the drain region immediately below the source region 3 in FIG. 10 regarding the state of point A and the state of point C in FIG. The horizontal axis of the graph is the linear axis showing the hole concentration, and the vertical axis is the position.
The upper part corresponds to the source region 3 and the lower part corresponds to the substrate region 1. That is, in the situation like the point A in FIG. 11, the injected holes spread as shown by the solid line in FIG. 12 due to the diffusion phenomenon, and the entire drain region 2 is in the high injection level state, 2 has low resistance. The concentration distribution is higher on the surface and lower as it approaches the substrate region because the substrate region 1 has a slightly higher potential. However, when the drain potential rises and a situation like the point C in FIG. 11 is reached, the hole distribution in the drain region 2 becomes the distribution shown by the broken line in FIG. 12, and the drain region close to the substrate region 1 In 2, a region which is not in a high injection level state appears. Since the region where the conductivity is not modulated spreads in the drain region 2 as the drain potential increases, the resistance of the device increases as the drain potential increases. It is to be noted that the drain region of such a vertical device is entirely depleted, the base region of the bipolar transistor is activated, and the current value is saturated in a region having a higher drain potential, which is indicated by point C in FIG. Such a region is called "pseudo saturation region".

Further, considering the turn-off of this element, in order to change this element from the conductive state to the cut-off state, the potential of the injection electrode 18, that is, the p-type injector region 8 is changed to the negative potential. Then, p-type injector region 8
In addition to stopping the injection of holes, the excess holes in the drain region 2 flow out to the p-type injector region 8, but the main current continues to flow until the excess hole density decreases to some extent. That is, this time is called an accumulation time, and at an operating point such as point A in the figure, this becomes long and rapid switching cannot be performed. Therefore, considering both the main current flowing with low loss and quick switching, the operating point of this device is point B in FIG.
It is desirable to use it in places such as.

In the structure as described above, it is better that the main current can be made to flow with a small control current (injector current). For such an improvement, the structure of the conventional example as shown in FIGS. Had the following limitations.

If the value of the drain potential at the point (point B) at which the current curve of FIG. 11 shifts from the linear region to the pseudo saturation region is increased at a constant injection current value, a larger main current can eventually flow with low loss. You can, but there are the following measures, and each has its limits. In FIG. 10, most of the holes injected from the p-type injector region 8 eventually jump into the source region 3 or pair annihilate with the electrons in the drain region 2.

Therefore, first, by reducing the area of the source region 3 to limit the rate of holes jumping into the source region 3, a method of conducting conductivity modulation of the drain region 2 more efficiently with a small hole current. There is. However, there is a technical limit to forming the source region 3 in a small size, and if the area is made too small, the on-resistance rather increases, so that the optimum value naturally exists.

Secondly, if the distance between the source region 3 and the injector region 8 is too close, the holes injected from the injector region 8 are sufficiently diffused to the drain region 2 and the conductivity thereof is increased. It flows away to the source region 3 without modulation, and conversely, if it is separated too much, the conductivity of the drain region 2 directly below the source region 3 which is the main current path of the main is due to recombination in the drain region 2 on the way. It cannot be increased effectively. Further, since the thickness of the drain region 2 is substantially regulated by the breakdown voltage of the device, there is an optimum value in these geometrical arrangements.

[0015]

As described above, in the conventional structure, there is a limit to the measures for expanding the linear region of the current characteristics of the device by changing the distance and size of each region. The present invention focuses on such problems and aims to provide a current control type element having a wide linear region.

[0016]

In order to achieve the above object, the present invention has a structure as set forth in the claims. That is, in the invention described in claim 1, the basic semiconductor device is such that the source region of the same conductivity type is provided on the surface of the drain region (for example, n-type) that is the substrate, and the cross-sectional shape is U-shaped. The fixed potential insulated electrode having the above structure is installed so as to sandwich the source region.
Here, the drain region sandwiched by the fixed potential insulating electrodes becomes the channel region. The fixed potential insulating electrode is kept at the same potential as the source electrode and is made of a material having a work function such as forming a depletion layer in the drain region and the channel region which are in contact with each other, for example, a p-type polycrystalline semiconductor here. Furthermore, contact the drain region and the insulating film of the fixed potential insulating electrode,
In this structure, an injector region of opposite conductivity type, which is not in contact with the source region, is provided.

That is, when the device is cut off, the depletion layer formed by the fixed potential insulating electrode forms a potential barrier for majority carriers (here, conduction electrons) in the channel region, and the source region and the drain region are electrically connected. It has been cut off. Furthermore, by applying an appropriate predetermined potential to the injector region from the outside during conduction, and introducing minority carriers (holes here) to the insulating film interface of the fixed potential insulating electrode in contact with the injector region, fixed potential insulation is achieved. The electric field from the p-type polycrystalline semiconductor of the electrode to the n-type channel region is shielded, and the potential barrier formed by the depletion layer is reduced or eliminated to open the channel. Furthermore, the conductivity of the drain region is improved by injecting holes from the injector region into the drain region.

In the semiconductor device having such a structure, the surface of the semiconductor substrate , which is a main path for holes (minority carriers) injected from the injector region to the n-type region, is further provided.
From the source region to the injector region along the direction of the channel region of (for example, corresponding to a in FIGS. 1 and 3 described later)
Is longer than the shortest distance between the source region and the injector region (e.g., corresponding to b in FIGS. 1 and 3 described later).

Further, in the invention described in claim 2, as means for realizing the invention described in claim 1,
The strip-shaped injector region and the linear fixed-potential insulated electrode in contact with the strip-shaped source region arranged in parallel with the strip-shaped injector region are in contact with the strip-shaped injector region at an angle other than a right angle.

Further, in the invention described in claim 3, as a means for realizing the invention described in claim 1, both sides in the length direction viewed from the surface of the semiconductor substrate are fixed.
The channel region sandwiched by the potential insulated electrodes and extending from the injector region to the source region has a curved, meandering, or spiral shape.

Further, in the invention described in claim 4, in the invention described in any one of claims 1 to 3, the main surface of the side wall of the groove in which the fixed potential insulated electrode exists is present there. The inversion layer formed at the interface of the insulating film has a plane orientation with high mobility.

Next, the operation will be described.

First, according to the structure described in claim 1, the minority carriers (here, holes) injected from the injector region in the conductive state of the element diffuse in the drain region to modulate the conductivity. Then, it eventually flows into the source region. By the way, in a situation where a large main current flows at a low drain potential, such as the point A in FIG. 11, the hole distribution in the drain region is different from that of the substrate region in the drain region as shown by the solid line in FIG. It exists at a high level up to the boundary. This means that in such a situation, the injector region and the substrate region are also in the forward bias state. Therefore, even if the drain potential increases, the potential of the injector region at that time must also be high in order to continue such a condition.
However, the main route of this injection current is the surface region of the element, that is, the channel region sandwiched between the fixed potential insulated electrodes, and the current injected when the potential of the injector region is increased in the structure of the conventional example. The value also increases.
Therefore, as described in claim 1, when the length of the channel region leading from the injector region to the source region, which is the main current path, is made longer than the shortest distance between the two, the current flowing from the injector region to the source region is The resistance increases, and the injected holes diffuse more effectively into the drain region. That is, when the injected current amount is the same, the point B where the current curve in FIG. 11 shifts from the linear region to the pseudo saturation region shifts to the higher side of the drain region, the linear region widens, and as a result, a large main current flows. Can be flowed with low loss.

Further, in a second aspect of the present invention, as means for realizing the first aspect of the present invention, a straight line is provided in a structure having a belt-shaped injector region and a source region arranged in parallel therewith. The fixed fixed-potential insulated electrode obliquely contacts the injector region, so that the channel region becomes longer than in the conventional example. For example, the angle is 45 °
, The length from the injector region to the source region along the fixed potential insulated electrode is about 1.4 times the shortest distance, and the resistance therebetween increases accordingly. This value is always greater than 1 if the two contact at an angle other than a right angle.

Further, in the invention described in claim 3,
As a means for realizing the invention of claim 1, the shape of the channel region sandwiched by the fixed potential insulated electrodes is curved or meandering or spiral, and the distance from the injector region to the source region is further reduced. It becomes longer and the resistance between them can be increased.

Further, in the invention described in claim 4,
In any one of claims 1 to 3,
This is a configuration that shortens the turn-off time. That is, when the semiconductor device is in the ON state, holes (minority carriers) are injected from the injector region into the drain region and the channel region, and excess carriers exist. However, when the turn-off signal is applied, the injector region, on the contrary, absorbs this excess minority carrier, and at that time, the minority carrier concentrates on the insulating film interface of the fixed insulating electrode to form the inversion layer, and the injector region Flows to. By selecting a plane orientation in which the mobility of the inversion layer is high at this time, quick turn-off is realized.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

1 to 4 are views showing a first embodiment of the present invention. 1 is a perspective view for explaining the basic structure of the device, FIG. 2 is a cross-sectional view showing the same part as the left front surface of FIG. 1, and FIG. 3 is a plan view of the device. It should be noted that FIG. 3 and FIG. 1 show a state in which the electrode (metal film) on the surface is removed. That is, FIG. 2 shows a cross section taken along a line perpendicular to the paper surface including the line segment AA ′ in FIG. In addition, FIG.
FIG. 5 is a cross-sectional view taken along a plane perpendicular to the plane of the drawing through a line segment BB ′ in the inside. In this embodiment, the semiconductor will be described as silicon.

The structure of the device will be described. 1 to 4, 1 is an n ⁺ type substrate region which is a substrate, 2 is an n type drain region, and 3 is an n ⁺ type source region. Also, 4 is MO
The S-type electrode is made of high-concentration p ⁺ -type polysilicon. A drain electrode 11 is in ohmic contact with the substrate region 1. 13 is a source electrode, which is the source region 3
Is in ohmic contact with the MOS type electrode 4. That is, the MOS electrode 4 is fixed at the source potential. Therefore, the MOS type electrode 4 and the insulating film 5 are collectively referred to as "fixed potential insulating electrode" 6. As shown in FIG. 2, the cross-sectional structure of the fixed potential insulating electrode 6 is formed in a groove whose side wall is substantially vertical like a letter "U".

Further, in FIG. 2, the drain region 2 sandwiched between the fixed potential insulating electrodes 6 will be referred to as a "channel region" 7. In this state, a depletion region is formed in the drain region 2 around the fixed potential insulating electrode 6 by the electric field resulting from the work function difference between the drain electrode 2 and the MOS type electrode 4. The depletion region forms a potential barrier against the conduction electrons forming the main current in the opened channel region 7, and the source region 3 and the drain region 2 are in a cutoff state as they are. Since the structure of the channel region forms this potential barrier, it is desirable to make the channel thickness H as narrow as possible. As an example, the channel thickness H is 2
It is about μm. Further, the channel length L shown in FIG. 2 is set to 2 to 3 times or more the channel thickness H so that the channel does not punch through even if the drain electric field is increased.

Furthermore, a p-type injector region 8 exists in a position in contact with the insulating film 5 and away from the source region 3. In FIG. 4, reference numeral 18 denotes an electrode which makes ohmic contact with the injector region 8 and is called an "injection electrode". Reference numeral 9 in FIG. 4 denotes an interlayer insulating film, and the broken line indicates the presence of a fixed potential insulating electrode in the depth direction of the paper surface, as can be seen from the relationship with FIG.

Further, in FIG. 3, in this embodiment, the fixed potential insulating electrode 6 has a linear side wall and is in contact with the p-type injector region 8 at an angle of 45 °. That is, the distance between the p-type injector region 8 and the source region 3 along the fixed potential insulated electrode 6 is about 1.4 times the linear distance.

Next, the operation will be described. In this element, for example, the source electrode 13 is grounded (at 0 V) and the drain electrode 1
1 is used by applying an appropriate positive potential via a load. First, when the injection electrode 18 is grounded, the device is in the cutoff state. Further, in this state, a depletion layer extends in the drain region 2 due to the drain potential. Of the minute amount of carriers generated in the depletion layer, conduction electrons flow through the n ⁺ type substrate region 1 to the drain electrode 11 as they are, and holes reach the interface of the insulating film 5 on the surface. But,
As a result, when the potential at the insulating film interface rises, the holes move to the p-type injector region 8 having a low potential in contact therewith, and flow away through the injection electrode 18. Therefore, the holes do not stagnate in the channel region 7, and the element keeps the cutoff state.

Next, although it is turned on, the potential of the injection electrode 18, that is, the potential of the p-type injector region 8 is increased by, for example, +.
When 0.5 V is applied, holes flow into the interface of the insulating film 5 in contact with the p-type injector region 8 contrary to the above, and raise the potential of the interface. Then, the holes block lines of electric force from the MOS electrode 4 to the channel region 7 and lower the potential barrier in the channel region 7. That is, this brings the drain region 2 and the source region 3 into conduction. When the potential of the injection electrode 18 is further increased, the pn junction composed of the p-type injector region 8 and the surrounding n-type region is forward-biased, and holes are directly transferred to the drain region 2.
And into the channel region 7. Then, the impurity concentration is made thin to maintain the breakdown voltage, and the conductivity of these n-type regions, which have been made to have high resistance, is increased, and the current flows with low resistance. Since the channel region 7 is used as a hole conduction path in this manner, the fixed potential insulated electrode 6 is formed as shown in FIG.
~ It is formed in a stripe shape as shown in Fig. 3.

Once the current flows in this way, this element can be regarded as a current control type element. A current-voltage curve with a constant injection current has the same shape as that of a vertical bipolar transistor as shown in FIG. 11, for example. That is, when the drain potential is low, the current curve shows a steep slope almost in proportion to the drain potential (linear region), but when the drain potential becomes high, the slope of the current curve becomes extremely dull (pseudo saturation region). ),
Further, the current value is almost saturated where the drain potential is high.

When this element is used as a switching device having a high current capacity, the operating point is as shown by point A in FIG. 11, and the power loss in the element is smaller when the drain potential is as low as possible. Good. Also, point C
When operated in such a state, a larger current can flow, but the power loss in the element becomes several times. By the way, FIG. 12 is a graph schematically explaining the hole density distribution in the drain region immediately below the source region 3 in FIG. 10 regarding the state of point A and the state of point C in FIG.
The horizontal axis of the graph is a linear axis showing the hole concentration, the vertical axis shows the position, and the upper portion corresponds to the source region 3 and the lower portion corresponds to the substrate region 1 corresponding to FIG. That is, in the situation like the point A in FIG.
As indicated by the solid line in 2, the drain region 2 has a low resistance, with the entire drain region 2 being in a high implantation level state.

The concentration distribution is high on the surface and decreases as it approaches the substrate region because the substrate region 1 has a slightly higher potential. However, when the drain potential rises and a situation like the point C in FIG. 11 is reached, the hole distribution in the drain region 2 becomes the distribution shown by the broken line in FIG. 12, and the drain region close to the substrate region 1 Shows a region that is not in a high injection level state. Since the region where the conductivity is not modulated expands the drain region as the drain potential increases, the resistance of the device increases as the drain potential increases. It is to be noted that the drain region of such a vertical device is entirely depleted, the base region of the bipolar transistor is activated, and the current value is saturated in a region having a higher drain potential, which is indicated by point C in FIG. Such a region is called "pseudo saturation region".

Further, considering the turn-off of this element, the potential of the injection electrode 18, that is, the p-type injector region 8 is changed to negative in order to change this element from the conductive state to the cutoff state. Then, p-type injector region 8
In addition to stopping the injection of holes from the drain region, excess holes in the drain region flow out to the p-type injector region 8.
The main current continues to flow until the excess hole density decreases to some extent. That is, this time is called an accumulation time, and at an operating point such as point A in the figure, this becomes long and quick switching cannot be performed. Therefore, considering both the main current flowing with low loss and quick switching, the operating point of this device is point B in FIG.
It is desirable to use it in places such as. By the way, in a situation where a large main current flows at a low drain potential, such as point A in FIG. 11, the hole distribution in the drain region is near the boundary between the drain region 2 and the substrate region as shown by the solid line in FIG. Exists at a high level. This means that in such a situation, the injector region and the substrate region are also in the forward bias state. Therefore, in order to continue such a condition even if the drain potential rises,
The potential of the injector region 8 at that time must also be high. However, the injection current flows through the drain region 2 along the surface channel region 7 along the solid line arrow a rather than along the solid line arrow b in FIG. 1 or 3, for example. This tendency becomes stronger as the drain potential becomes higher. In the structure shown in FIG. 7 which is a conventional example, the lengths of the two current paths are substantially the same or the solid arrow a is shorter. That is, the electric current was flowing more to the surface side. Therefore, if the potential of the injector region 8 is increased, the injected current value also increases, but in the present embodiment, the fixed potential insulating electrode is longer than the shortest distance between the injector region 8 and the source region 3. Since the length along 6 is 1.4 times longer, the resistance component when current flows from the injector region 8 to the source region 3 rises, and the injected holes are more effective in the drain region 2. Diffuse inward. That is, when the amount of injected current is the same, the point B where the current curve in FIG. 11 shifts from the linear region to the pseudo saturation region shifts to the higher side of the drain region 2 and the linear region widens, resulting in a large main area. Current can be passed with low loss. Further, in FIG. 2, the angle formed between the injector region 8 and the side wall of the fixed potential insulated electrode 6 is 45 °,
If the angle is other than a right angle, the length along the injector region 8 and the fixed potential insulated electrode 6 becomes longer than the shortest distance, which is effective.

Furthermore, this is the point corresponding to the above-mentioned claim 4, and in the present structure, for example, the line segment BB ′ in FIG. 3 is used.
Aligning the side surface of the fixed potential insulated electrode 6 along with the (110) plane of silicon has the following effects. That is, in the ON state of this structure, holes are present at a high concentration in both the drain region 2 and the channel region 7, and the conductivity of these regions is high. But,
Once turned off and a negative potential is applied to the injector region 8, the supply of holes from the injector region 8 is stopped, and conversely, excess minority carriers flow into the injector region 8. At this moment, all the excess carriers in the channel region 7 move to the interface of the insulating film to form an inversion layer. Since the inversion layer has the same negative potential as that of the injector region 8, the drain region 2 in the surroundings is affected. The existing excess carriers are also attracted to the interface of the insulating film, and eventually flow out of the element through the injector region 8. That is, at this time, the turn-off time of the device is shortened by selecting a crystal plane orientation having high mobility for the inversion layer formed at the interface of the insulating film.

Next, FIG. 5 is a plan view showing a second embodiment of the present invention, which is a plan view corresponding to FIG.
This corresponds to claim 3 above. In the present embodiment, since the shape of the channel region 7 serving as a hole conduction path is connected from the injector region 8 to the source region 3 while meandering, the hole region is further formed as compared with the first embodiment. Higher resistance to current. Further, by increasing the number of meandering, the length of the hole passage can be adjusted more freely than in the first embodiment. Further, here, regarding the width of the meandering, the density of the source regions 3 in FIG. 5 is smaller than the density in FIG. However, in the case of such a dot-shaped source region 3, the source region 3 does not need to exist for each channel region 7 as shown in FIG. 2, and if the distance from the source region 3 to the substrate region 1 is D. It has been confirmed by numerical calculation and experiments that the ON resistance is hardly affected if the surface region exists at intervals of 2D. Therefore, along with this, the amplitude of the meandering may be within the width D.

Next, FIG. 6 shows another embodiment. This is a spiral shape of the channel region 7 along the fixed potential insulated electrode 6. The distance from the injector region 8 to the source region 3 has an optimum value for effectively conductivity-modulating the drain region 2. When the value is longer than the distance D from the source region 3 to the substrate region 1 in the depth direction, it is better to form the fixed potential insulating electrode 6 in a meandering or spiral shape in such a direction. A long conduction path can be taken. Further, also in FIGS. 5 and 6 described above, by selecting the plane orientation of the side wall of the fixed potential insulating electrode 6 to be a plane having high mobility for the inversion layer, the turn-off can be performed quickly as in the first embodiment. Is possible.

[0042]

As described above, according to the present invention, a large main current can be controlled with a smaller control current as compared with the structure of the conventional semiconductor device. Further, according to the fourth aspect, it is possible to quickly turn off.

[Brief description of drawings]

FIG. 1 is a perspective view of an element according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the element according to the first embodiment of the present invention.

FIG. 3 is a plan view of the element according to the first embodiment of the present invention.

FIG. 4 is another cross-sectional view of the element according to the first embodiment of the present invention.

FIG. 5 is a plan view of an element showing a second embodiment of the present invention.

FIG. 6 is another plan view showing the second embodiment of the present invention.

FIG. 7 is a perspective view of a conventional example.

FIG. 8 is a sectional view of a conventional example.

FIG. 9 is a plan view showing a surface structure in a conventional example.

FIG. 10 is a sectional view of the conventional example seen from another angle.

FIG. 11 is a current / voltage characteristic diagram of a semiconductor device of a conventional example.

FIG. 12 is a characteristic diagram showing a hole distribution in a drain region in a conductive state in a semiconductor device of a conventional example.

[Explanation of symbols]

1 ... N ⁺ type substrate region 7 ... Channel region 2 ... N type drain region 8 ... P type injector region 3 ... N ⁺ source region 9 ... Interlayer insulating film 4 ... MOS type electrode 11 ... Drain electrode 5 ... Insulating film 13 ... Source Electrode 6 ... Fixed potential insulating electrode 18 ... Injection electrode a ... Distance from p type injector region 8 to n ⁺ source region 3 along the interface of fixed potential insulating electrode 6 ... P type injector region 8 and n ⁺ source region 3 Shortest distance to

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Claims (4)

(57) [Claims] 1. One or more island-shaped source regions of the same conductivity type are provided in contact with one main surface of a one conductivity type semiconductor substrate that is a drain region, and the source region is sandwiched between the main surfaces. A fixed potential insulating electrode insulated from the drain region by an insulating film and kept at the same potential as the source region, the fixed potential insulating electrode having one or a plurality of trenches. The electrode is made of a conductive material having a work function so as to form a depletion region in the drain region adjacent to the drain region through the insulating film, and is a part of the drain region in contact with the source region, and the fixed potential insulation A channel region sandwiched by electrodes, and the channel region has a multi-region between the source region and the neutral drain region due to the depletion region formed around the fixed potential insulated electrode. A potential barrier for preventing the movement of carriers is formed, and further, minority carriers are introduced into the interface of the insulating film surrounding the fixed potential insulating electrode to form an inversion layer, and the fixed potential insulating electrode is connected to the drain region. Of the opposite conductivity type in contact with the insulating film and the drain region but not with the source region in order to shield the electric field to and reduce or eliminate the potential barrier formed in the channel region to open the channel. In a semiconductor device having an injector region, along the channel region direction of the semiconductor substrate surface ,
The semiconductor device, wherein the length from the source region to the injector region is longer than the shortest distance between the source region and the injector region. 2. The fixed potential insulated electrode having the strip-shaped injector region and the strip-shaped source region arranged in parallel with the injector region and extending from the injector region to the source region. 2. The semiconductor device according to claim 1, wherein the side wall of the semiconductor device is linear and is in contact with the belt-shaped injector region at an angle other than a right angle. 3. The channel region, which is sandwiched between the fixed potential insulating electrodes on both sides in the length direction when viewed from the surface of the semiconductor substrate , and which connects the source region to the injector region, is curved or meandering. Alternatively, the semiconductor device according to claim 1, wherein the semiconductor device has a spiral shape. 4. The side wall of the groove having the interface of the insulating film is formed with a crystal plane orientation having a high mobility for the inversion layer formed by the minority carriers introduced from the injector region. The semiconductor device according to any one of claims 1 to 3.