JP3508249B2 - Semiconductor dynamic quantity sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a semiconductor dynamic quantity sensor suitable for use in, for example, a vehicle body control system or a navigation system of an automobile.

[0002]

2. Description of the Related Art As is well known, a mechanical quantity sensor such as a yaw rate sensor or an acceleration sensor is used in a vehicle body control system or a navigation system of an automobile. Among them, as a yaw rate sensor, conventionally,
For example, as disclosed in JP-A-2-223817, a structure in which a vibrating body in which a piezoelectric element is bonded to a specific surface of a metal square rod is supported by a thin rod, or JP-A-4-1424 is used.
As disclosed in Japanese Patent Laid-Open No. 20, a structure having a piezoelectric tuning element bonded to a metal tuning fork has been considered.

In each of these yaw rate sensors, a piezoelectric element vibrates the body to detect the distortion caused by the Coriolis force generated by the yaw rate, which is the object of measurement, by the change in the voltage detected by the piezoelectric element. It is what

However, in the yaw rate sensor having this kind of structure, the performance such as the detection sensitivity depends on the supporting method of the vibrating body, the processing accuracy and the like. For this reason, the high-performance yaw rate sensor is inevitably expensive because the difficulty in processing and assembling the yaw rate sensor increases. In addition, it is the current situation that miniaturization of the yaw rate sensor cannot be easily realized due to restrictions in processing and assembly.

Therefore, in recent years, a transistor type yaw rate sensor as disclosed in Japanese Patent Application No. 5-311762 has been proposed as a yaw rate sensor which has high performance and is inexpensive and can be easily downsized. There is. Figure 9
Shows the planar structure of this transistor type yaw rate sensor, and FIG. 10 shows the transistor detection unit A shown in FIG.
11 shows an enlarged state, and FIG. 11 shows a sectional structure of a portion corresponding to line aa in FIG.

That is, four anchor portions 1 are provided on a semiconductor substrate 11 formed of a P-type silicon substrate.
21 to 124 are formed, and each anchor portion 121 to
Beams 131 to 134 whose one ends are respectively supported by 124
The weight 14 is supported by. The weight 14 has a strip-shaped movable electrode 15 for a gate, which is provided so as to project from the pair of opposite sides in the left-right direction.
1, 152 are integrally formed. The weight 14 is integrally formed with excitation electrodes 161 to 164 on both sides of each of the gate movable electrodes 151 and 152, in which a pair of strips are provided so as to project in parallel with each other in the shape of comb teeth. .

Here, in the portion of the main surface of the semiconductor substrate 11 corresponding to the gate movable electrodes 151, 152, the source electrode 17 made of an N-type impurity diffusion layer is formed.
1, 172 and drain electrodes 181, 182 are formed. The gate movable electrode 151, the source electrode 171, and the drain electrode 181 form the transistor detection unit A having the air gap 19. In the transistor detection unit A, when a voltage is applied between the gate movable electrode 151 and the semiconductor substrate 11, an inversion layer is formed in the channel region 20 between the source electrode 171 and the drain electrode 181, and a current flows. .

The transistor detecting section B including the gate movable electrode 152, the source electrode 172 and the drain electrode 182 is the same as the transistor detecting section A, and therefore its explanation is omitted. In addition, the semiconductor substrate 1
A lower electrode 21 is formed on a portion of the main surface of No. 1 facing the beams 131 to 134 and the weight 14. The lower electrode 21 is set to the same potential as the beams 131 to 134, the weight 14, and the gate movable electrodes 151 and 152, thereby preventing an electrostatic force generated between the lower electrode 21 and the semiconductor substrate 11. Further, on the main surface of the semiconductor substrate 11, the source electrodes 171, 172 and the drain electrodes 181, 18 are formed.
A LOCOS oxide film 22 for separating the lower electrode 21 from the lower electrode 21 is formed.

Further, on the main surface of the semiconductor substrate 11,
Fixed electrodes 231 to 234 for excitation are formed corresponding to the electrodes 161 to 164 for excitation, respectively. These excitation fixed electrodes 231 to 234 are configured such that the three strips each formed in the shape of a comb tooth are arbitrarily combined with a pair of strips constituting the excitation electrodes 161 to 164, respectively. There is. Then, by applying an AC voltage of a predetermined frequency between the excitation electrodes 161 to 164 and the excitation fixed electrodes 231 to 234, the excitation electrodes 161 to 164 are generated by the electrostatic force generated between the comb-shaped electrodes. It is vibrated, and by extension, the weight 14 and the gate movable electrodes 151, 1
52 is excited.

In this state, when a yaw rate is generated on the axis ω shown in FIG. 9, Coriolis force is generated in proportion to the speed of excitation and its weight, and the gate 14 and the gate movable electrodes 151 and 152 are generated. It is displaced in a direction perpendicular to the surface of the semiconductor substrate 11. The air gap 19 changes due to this displacement, and the electric field strength applied to the channel region 20 changes, so that the concentration of the inversion layer in the channel region 20 changes and a current change occurs. In short, the transistor type yaw rate sensor generates the Coriolis force at the yaw rate, and the source electrodes 171, 172 and the drain electrode 181, which are generated by the displacement of the gate movable electrodes 151, 152.
The yaw rate is detected based on the change in current between 182.

This transistor type yaw rate sensor is
Impurities are diffused into the semiconductor substrate 11 to form the source electrode 171,
172 and the first to form the drain electrodes 181, 182
Step, a second step of forming a sacrificial layer (not shown) on the main surface of the semiconductor substrate 11, beam-shaped gate movable electrodes 151, 152 and the gate movable electrode 151, on the sacrificial layer.
Exciting fixed electrodes 231 to 23 for vibrating 152
And the gate movable electrode 15
The gate movable electrodes 151, 15 are arranged so that the change in current between the source electrodes 171, 172 and the drain electrodes 181, 182 due to the displacement of 1, 152 can be detected.
And a fourth step of etching away the sacrificial layer underneath.

However, in the conventional transistor type yaw rate sensor as described above, the source electrodes 171 and 1
72 and the drain electrodes 181, 182 and the lower electrode 21 are separated from each other by the LOCOS oxide film 22 facing the movable electrodes 151, 152 for gates, so that the source electrodes 171 and 172 and the drain electrodes 181 and 182 are separated from each other. When a voltage is applied to the gate movable electrodes 151 and 152 in order to pass a current between them, an electrostatic force is generated between the gate movable electrodes 151 and 152 and the LOCOS oxide film 22, which are normally 0 V, and the gate is moved. The gap between the movable electrodes 151 and 152 for semiconductors and the semiconductor substrate 11 becomes unnecessarily small, and in the worst case, the movable electrodes 151 and 152 for gates adhere to the semiconductor substrate 11.

On the other hand, as an acceleration sensor, conventionally,
MISF as disclosed in Japanese Patent Laid-Open No. 4-25764
An ET type acceleration sensor has been developed. 12 shows a planar structure of this MISFET type acceleration sensor, and FIG. 13 shows a sectional structure of a portion corresponding to line bb of FIG.

That is, when the gate electrode 25 held on the acceleration detecting substrate 24 via the beam-like portion is displaced vertically in the figure due to the acceleration, the channel formed in the P-type semiconductor substrate 26 is formed. The carrier concentration in the area changes,
The acceleration is detected by utilizing the fact that the current flowing between the source electrode 27 and the drain electrode 28 increases or decreases. 12 and 13, reference numeral 2
Reference numeral 9 is a weight, reference numeral 30 is a groove, and reference numerals 311 to 311.
Reference numeral 13 is a wiring path, and reference numeral 32 is a package.

However, since such a MISFET type acceleration sensor is manufactured by processing bulk silicon, it has a disadvantage that it is difficult to reduce its size and cost due to problems such as processing accuracy of silicon. There is.

Therefore, recently, as a small-sized and low-cost acceleration sensor, a transistor type acceleration sensor utilizing a surface micromachining technique has been proposed as shown in Japanese Patent Application No. 5-322348. 14 shows a planar structure of an acceleration sensor using this surface micromachining technique, FIG. 15 shows an enlarged state of the transistor detection unit C shown in FIG. 14, and FIG.
The cross-sectional structure of the portion corresponding to line c-c is shown.

That is, the four anchor portions 341 to 344 formed on the semiconductor substrate 33 have beams 351 to 35.
A weight 36 is supported via the number 4. The weight 36 is integrally formed with strip-shaped gate movable electrodes 371 and 372 so as to project laterally from a pair of opposing side portions.

Here, source electrodes 381 and 382 and drain electrodes 391 and 392 are formed on portions of the main surface of the semiconductor substrate 33 corresponding to the gate movable electrodes 371 and 372, respectively. Then, the gate movable electrode 371, the source electrode 381 and the drain electrode 3
91 constitutes the transistor detection section C having the air gap 40. This transistor detector C
By applying a voltage between the gate movable electrode 371 and the semiconductor substrate 33, an inversion layer is formed in the channel region 41 between the source electrode 381 and the drain electrode 391, and a current flows.

Since the transistor detection section D including the gate movable electrode 372, the source electrode 382 and the drain electrode 392 is similar to the transistor detection section C, the description thereof will be omitted. In addition, the semiconductor substrate 3
A lower electrode 42 is formed on a portion of the main surface of No. 3 that faces the beams 351 to 354 and the weight 36. The lower electrode 42 is set to the same potential as the beams 351 to 354, the weight 36, and the gate movable electrodes 371 and 372, thereby preventing an electrostatic force generated between the lower electrode 42 and the semiconductor substrate 33. Further, on the main surface of the semiconductor substrate 33, the source electrodes 381 and 382 and the drain electrodes 391 and 39.
A LOCOS oxide film 43 for separating the lower electrode 42 from the second electrode is formed.

In this acceleration sensor, the air gap 40 between the gate movable electrodes 371 and 372 and the surface of the semiconductor substrate 33 changes in response to the acceleration in the direction perpendicular to the surface of the semiconductor substrate 33. The electric field strength applied to 41 changes, and the acceleration is detected based on the change in the current. For the acceleration in the horizontal direction with respect to the surface of the semiconductor substrate 33, the gate movable electrodes 371 and 372 are displaced in the horizontal direction. , The gate widths of the transistor detectors C and D change, and the acceleration is detected based on the current change.

However, even in the conventional acceleration sensor as described above, L for separating the source electrode 381, 382 and the drain electrode 391, 392 from the lower electrode 42.
The OCOS oxide film 43 forms the gate movable electrodes 371, 37.
2 facing each other, the gate movable electrodes 371, 37
2 and the LOCOS oxide film 43, the electrostatic force generated between the gate movable electrodes 371 and 372 and the semiconductor substrate 33 narrows the gap more than necessary, and in the worst case,
The problem arises that the gate movable electrodes 371 and 372 are attached to the semiconductor substrate 33.

[0022]

As described above, in the conventional semiconductor mechanical quantity sensor represented by the transistor type yaw rate sensor and the acceleration sensor utilizing the surface micromachining technology, the gate movable electrode and the LOCOS are used.
Due to the electrostatic force generated due to the fact that the oxide film faces each other, the gap between the gate movable electrode and the semiconductor substrate tends to be narrower than necessary, and the gate movable electrode may adhere to the semiconductor substrate. Have

Therefore, the present invention has been made in consideration of the above circumstances, and suppresses the generation of electrostatic force in a region that does not contribute to the detection of a mechanical quantity, and keeps the movable gate electrode and the semiconductor substrate at a normal distance. An object is to provide an extremely good semiconductor dynamic quantity sensor to be obtained.

[0024]

SUMMARY OF THE INVENTION A semiconductor dynamic quantity sensor according to the present invention comprises a semiconductor substrate, a movable electrode which is supported by a beam structure at a predetermined distance from the surface of the semiconductor substrate, and a surface of the semiconductor substrate. a source electrode and a drain electrode formed by impurity diffusion in a position facing the movable electrode, at a position facing the movable electrode on the surface of the semiconductor substrate
There are a lower electrode and formed by impurity diffusion in a position other than the source electrode and the drain electrode, and an electrically insulating LOCOS oxide film and a source electrode and a drain electrode and a lower electrode formed on a surface of a semiconductor substrate A dynamic quantity is detected by a change in current between a source electrode and a drain electrode caused by displacement of the movable electrode, and the movable electrode is arranged at a position not facing the LOCOS oxide film.

Further, the semiconductor mechanical quantity sensor according to the present invention includes a semiconductor substrate, a movable electrode supported by the beam structure at a predetermined distance from the surface of the semiconductor substrate, and a surface of the semiconductor substrate facing the movable electrode. a source electrode and a drain electrode formed by impurity diffusion in a position, a position facing the movable electrode on the surface of the semiconductor substrate,且
And a LOCOS oxide film that is formed on the surface of the semiconductor substrate and electrically insulates the source electrode and the drain electrode from the lower electrode. The dynamic quantity is detected by the change in the current between the source electrode and the drain electrode caused by the displacement of the electrode.
A part of the region facing the COS oxide film is deleted.

[0026]

With the above arrangement, the movable electrode is LOC'd.
Since it is arranged at a position not facing the OS oxide film, it is possible to prevent electrostatic force from being generated due to the potential difference between the movable electrode and the LOCOS oxide film.
The movable electrode and the semiconductor substrate can be held at a normal distance. Further, since a part of the region of the movable electrode facing the LOCOS oxide film is removed, it is possible to reduce the generation of electrostatic force between the movable electrode and the LOCOS oxide film.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a transistor type yaw rate sensor will be described in detail below with reference to the drawings. FIG. 1 shows a planar structure of the transistor type yaw rate sensor described in this embodiment. That is, reference numeral 44 is a semiconductor substrate, which is formed of a P-type silicon substrate. Four anchor portions 451 to 454 are formed on the semiconductor substrate 44, and the weight 47 is supported by the beams 461 to 464 whose one ends are supported by the anchor portions 451 to 454, respectively.

The weight 47 has a pair of support pieces 481 and 481 protruding in parallel from the upper side in the figure, and a movable gate electrode 491 is supported so as to be installed between the support pieces 481 and 481. Has been done. Also, this weight 47
A pair of support pieces 482 and 482 are provided in parallel with each other from the lower side in the figure, and the gate movable electrode 492 is supported so as to be bridged between these support pieces 482 and 482.

The weight 47 is a movable electrode 49 for a gate.
It is configured as a main body mechanism of 1,492, and is installed to obtain a displacement amount due to the yaw rate. Also,
The weight 47 is integrally formed with excitation electrodes 501 to 504, each of which is formed by a pair of strips projecting parallel to each other in a comb tooth shape from a pair of opposing sides in the left-right direction in the drawing. ing. These excitation electrodes 501 to 504 have a weight 47.
It also serves to give vibration to the gate movable electrodes 491 and 492.

Then, the anchor portions 451-454,
Beams 461-464, weight 47, support pieces 481, 482
Movable electrodes for gate 491, 492 and electrode for excitation 501
˜504 are integrally formed of a heat resistant metal such as polysilicon or tungsten.

In this embodiment, polysilicon is used as a typical material. Furthermore, the weight 47, the support pieces 481 and 482, the gate movable electrodes 491 and 492, and the excitation electrodes 501 to 504 are anchors so as to be separated from the main surface of the semiconductor substrate 44 by a predetermined distance (air gap L). It is supported by the portions 451 to 454 and the beams 461 to 464.

Here, on the main surface of the semiconductor substrate 44, an N-type impurity is applied to the semiconductor substrate 44 made of a P-type silicon substrate by means of ion implantation or the like so as to be orthogonal to the gate movable electrodes 491 and 492, respectively. Source electrodes 511 and 512 and drain electrodes 521 and 522 are formed by the diffusion layer formed by introducing.

The gate movable electrode 491, the source electrode 511 and the drain electrode 521 are connected to the air gap L.
Is included in the transistor detection unit E. In the transistor detection unit E, an inversion layer is formed in the channel region 53 between the source electrode 511 and the drain electrode 521 by applying a voltage between the gate movable electrode 491 and the semiconductor substrate 44, and a current flows. .

The transistor detecting section F including the gate movable electrode 492, the source electrode 512 and the drain electrode 522 is the same as the transistor detecting section E, and the description thereof is omitted. In addition, the semiconductor substrate 4
Impurities are introduced into portions of the main surface of No. 4 of the beams 461 to 464, the weight 47, the support pieces 481 and 482, the movable electrodes for gates 491 and 492, and the electrodes for excitation 501 to 504 corresponding to the vibrating range. The lower electrode 54 formed of the formed diffusion layer is formed.

The lower electrode 54 includes beams 461-464,
Weight 47, support pieces 481, 482, gate movable electrode 4
91, 492 and the excitation electrodes 501 to 504 are set to the same potential to prevent generation of electrostatic force between the semiconductor substrate 44 and the weight 47, the support pieces 481, 4.
82, the gate movable electrodes 491 and 492, the excitation electrodes 501 to 504, etc. are prevented from adhering to the semiconductor substrate 44.

On the main surface of the semiconductor substrate 44,
Excitation fixed electrodes 551 to 554 made of polysilicon are arranged corresponding to the excitation electrodes 501 to 504, respectively. These excitation fixed electrodes 551 to 554
Are fixedly installed at the same height positions as the excitation electrodes 501 to 504 on the main surface of the semiconductor substrate 44.

In this case, the excitation fixed electrodes 551 to 55
Reference numeral 4 has three strips each formed in the shape of a comb tooth, and one strip in the center is arranged at the center position of a pair of strips forming the excitation electrodes 501 to 504, respectively. At the same time, the other two strips are arranged so as to be located outside the pair of strips, respectively, so that the comb teeth are combined with each other. A predetermined gap is formed in the.

By applying an AC voltage of a predetermined frequency between the excitation electrodes 501 to 504 and the excitation fixed electrodes 551 to 554, the excitation electrode 501 is generated by the electrostatic force generated between the comb-teeth electrodes. ~ 504 is vibrated,
As a result, the weight 47 and the gate movable electrodes 491, 492.
Vibration is applied to. In this case, two excitation electrodes 501, 503 and 502, 5 are installed on each side of the weight 47.
04 and 04 are given a potential difference that is 180 ° out of phase with each other.

The gate movable electrodes 491, 49
2 is the gate width of the transistor detection portions E and F, that is, the source electrodes 511 and 512 and the drain electrode 52 even during the maximum horizontal vibration with respect to the surface of the semiconductor substrate 44.
The length is set so that the overlapping area with 1,522 does not change. In other words, the supporting pieces 481 and 482 are set so as not to overlap the source electrodes 511 and 512 and the drain electrodes 521 and 522 even at the time of maximum vibration.

The movable electrodes 491 and 492 for each gate
Are support pieces 481, 482, weights 47, and beams 461-46.
4 and the anchor portions 451 to 454, a wiring circuit (not shown) is connected to a detection circuit (not shown) formed on the semiconductor substrate 44. In addition, the semiconductor substrate 4
The source electrodes 511, 512, the drain electrodes 521, 522, the lower electrode 54, and the excitation fixed electrodes 551 to 554 formed on the semiconductor substrate 4 are also formed on the semiconductor substrate 44 via wiring paths (not shown) ( (Not shown).

Here, FIG. 2 shows a state in which the transistor detection portion E is enlarged. That is, the LOCOS oxide film 56 for electrically separating the source electrode 511, the drain electrode 521, and the lower electrode 54 is formed on the semiconductor substrate 44 on which the transistor detection unit E is formed. Then, the source electrode 511 and the drain electrode 5
21, the part where the LOCOS oxide film 56 is not formed becomes the channel region 53. Impurities are introduced into the channel region 53 so that the inversion layer is formed at a low voltage.

Here, the gate movable electrode 49 is used.
1 is installed at a position not facing the LOCOS oxide film 56. That is, since the gate movable electrode 491 is separated from the weight 47 by a predetermined distance by the pair of support pieces 481 and 481, the channel in which the LOCOS oxide film 56 is not formed between the source electrode 511 and the drain electrode 521 is formed. It is installed at a position facing the area 53.

Therefore, the gate movable electrode 491 and the LO
It is possible to prevent electrostatic force from being generated due to the potential difference between the COS oxide film 56 and the gate movable electrode 491 and the semiconductor substrate 44 to be held at a normal distance. In this case, it goes without saying that the gate movable electrode 491 is set so as not to overlap with the LOCOS oxide film 56 even during the maximum horizontal vibration with respect to the surface of the semiconductor substrate 44.

FIG. 3 shows a sectional structure of a portion corresponding to line dd in FIG. That is, as described above, the air gap L is formed between the gate movable electrode 491 and the semiconductor substrate 44. Movable electrode 491 for gate
By applying a voltage between the semiconductor substrate 44 and the semiconductor substrate 44,
The inversion layer is formed in the channel region 53, and the source electrode 51 is formed.
A current flows between 1 and the drain electrode 521.

Here, when an AC voltage having a predetermined frequency is applied between the excitation electrodes 501 to 504 and the excitation fixed electrodes 551 to 554, and the weight 47 is excited, the gate movable electrode 491 becomes 3 is excited in the direction indicated by the arrow. In this case, when the yaw rate is not generated,
The current value flowing between the source electrode 511 and the drain electrode 521 via the inversion layer of the channel region 53 is constant.

On the other hand, when the yaw rate is generated on the axis ω shown in FIG. 1, Coriolis force proportional to the excitation speed and the weight is generated, and the gate movable electrode 491 is displaced in the direction perpendicular to the surface of the semiconductor substrate 44 together with the weight 47. To do. Then, the air gap L is changed by this displacement, and the electric field strength applied to the channel region 53 is changed.
The concentration of the inversion layer in 3 changes, the current changes, and the yaw rate is detected.

FIG. 4A shows a sectional structure of a portion corresponding to line ee of FIG. 2, and FIG. 4B shows a sectional structure of a portion corresponding to line ff of FIG. ing. In each case, it was found that the gate movable electrode 491 did not face the LOCOS oxide film 56, and the gate movable electrode 491 and the LO movable electrode 491 did not face each other.
It is understood that the generation of the electrostatic force between the COS oxide film 56 is prevented and the movable electrode for gate 491 and the semiconductor substrate 44 are held at a normal distance.

FIG. 5 shows a sectional structure of a portion corresponding to the line gg in FIG. That is, the anchor portions 451 and 453 are formed on the insulating film 57 formed on the surface of the semiconductor substrate 44.
Are fixed, and thereby an air gap L is formed. The insulating film 57 is formed of, for example, an oxide film or a nitride film.

FIG. 6 shows a sectional structure of a portion corresponding to the line hh in FIG. That is, the excitation fixed electrode 551 is fixed on the insulating film 57 formed on the surface of the semiconductor substrate 44, so that the excitation fixed electrode 551 is installed at the same height position as the excitation electrode 501. become.

Therefore, according to the structure of the above embodiment, the gate movable electrode 491 is connected to the pair of support pieces 481.
Since the gate movable electrode 491 is arranged at a position not facing the LOCOS oxide film 56 by being separated from the weight 47 by a predetermined distance by 481, the potential difference between the gate movable electrode 491 and the LOCOS oxide film 56 is caused. Generation of electrostatic force can be prevented, and the gate movable electrode 491 and the semiconductor substrate 44 can be held at a normal distance.

Next, FIG. 7 shows another embodiment of the present invention, which is applied to the transistor type acceleration sensor shown in FIG. That is, in FIG. 7, the same parts as those in FIG. 15 are designated by the same reference numerals, and the LOCOS oxide film 4 of the gate movable electrode 371 will be described.
3 is partially removed by forming the opening 58 so that the gate movable electrode 371 and the LO are removed.
The generation of electrostatic force between the COS oxide film 43 and the COS oxide film 43 is reduced.

Further, the LOCO of the gate movable electrode 371 is
As a means for reducing the generation of the electrostatic force by reducing a part of the region facing the S oxide film 43, as shown in FIG.
The width of the gate movable electrode 371 may be narrowed. Then, the LO of the gate movable electrode 371
When reducing a part of the region facing the COS oxide film 43, it is effective to make the deleted area larger than the undeleted area. The present invention is not limited to the above-described embodiments, but can be variously modified and implemented without departing from the scope of the invention.

[0053]

As described above in detail, according to the present invention,
It is possible to provide an extremely good semiconductor mechanical quantity sensor that can suppress the generation of electrostatic force in a region that does not contribute to the detection of mechanical quantity and can keep the movable electrode for gate and the semiconductor substrate at a normal distance.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a semiconductor physical quantity sensor according to the present invention.

FIG. 2 is an enlarged plan view showing a transistor detection unit in the embodiment.

FIG. 3 is a cross-sectional view of a portion corresponding to line dd in FIG.

FIG. 4 is a cross-sectional view of a portion corresponding to the ee line and the ff line of FIG.

5 is a cross-sectional view of a portion corresponding to line gg in FIG.

6 is a cross-sectional view of a portion corresponding to line hh in FIG.

FIG. 7 is a plan view showing another embodiment of the present invention.

FIG. 8 is a plan view showing a modified example of the other embodiment.

FIG. 9 is a plan view showing a conventional transistor type yaw rate sensor.

FIG. 10 is an enlarged plan view showing a transistor detection unit in the conventional sensor.

11 is a sectional view of a portion corresponding to the line aa in FIG.

FIG. 12 is a plan view showing a conventional acceleration sensor.

13 is a cross-sectional view of a portion corresponding to line bb of FIG.

FIG. 14 is a plan view showing a conventional transistor type acceleration sensor.

FIG. 15 is an enlarged plan view showing a transistor detection portion of the conventional sensor.

16 is a sectional view of a portion corresponding to line cc in FIG.

[Explanation of symbols]

11 ... Semiconductor substrate, 121-124 ... Anchor part, 13
1-134 ... Beam, 14 ... Weight, 151, 152 ... Movable electrode for gate, 161-164 ... Electrode for excitation, 171, 1
72 ... Source electrode, 181, 182 ... Drain electrode, 1
Reference numeral 9 ... Air gap, 20 ... Channel region, 21 ... Lower electrode, 22 ... LOCOS oxide film, 231-234 ... Excitation fixed electrode, 24 ... Acceleration detection substrate, 25 ... Gate electrode,
26 ... P-type semiconductor substrate, 27 ... Source electrode, 28 ... Drain electrode, 29 ... Weight, 30 ... Groove, 311 ... 313 ... Wiring path, 32 ... Package, 33 ... Semiconductor substrate, 341 ...
344 ... Anchor part, 351-354 ... Beam, 36 ... Weight, 371, 372 ... Gate movable electrode, 381, 38
2 ... Source electrode, 391, 392 ... Drain electrode, 40
... Air gap, 41 ... Channel region, 42 ... Lower electrode, 43 ... LOCOS oxide film, 44 ... Semiconductor substrate, 45
1-454 ... Anchor part, 461-464 ... Beam, 47 ...
Weights, 481, 482 ... Support pieces, 491, 492 ... Gate movable electrodes, 501-504 ... Excitation electrodes, 511,
512 ... Source electrode, 521, 522 ... Drain electrode,
53 ... Channel region, 54 ... Lower electrode, 551-554
... Exciting fixed electrode, 56 ... LOCOS oxide film, 57 ... Insulating film, 58 ... Opening, AF ... Transistor detecting section.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification code FI G01P 15/125 G01P 15/125 Z

Claims (6)

(57) [Claims] 1. A semiconductor substrate, a movable electrode supported on the semiconductor substrate by a beam structure at a predetermined distance from the surface of the semiconductor substrate, and formed by impurity diffusion at a position on the surface of the semiconductor substrate facing the movable electrode. A source electrode and a drain electrode, and at a position facing the movable electrode on the surface of the semiconductor substrate.
LOC there are, and to electrically insulate the lower electrode formed by impurity diffusion, the formed surface of the semiconductor substrate between the source electrode and the drain electrode and the lower electrode in a position other than the source electrode and the drain electrode
An OS oxide film is provided, and a mechanical quantity is detected by a current change between the source electrode and the drain electrode caused by displacement of the movable electrode. The movable electrode is installed at a position not facing the LOCOS oxide film. A semiconductor dynamical quantity sensor having the above structure. 2. The semiconductor dynamic quantity sensor according to claim 1, wherein the movable electrode is installed so as not to face the LOCOS oxide film in the entire displacement range. 3. A semiconductor substrate, a movable electrode supported on the semiconductor substrate by a beam structure at a predetermined distance from the surface of the semiconductor substrate, and formed by impurity diffusion on a surface of the semiconductor substrate facing the movable electrode. A source electrode and a drain electrode, and at a position facing the movable electrode on the surface of the semiconductor substrate.
LOC there are, and to electrically insulate the lower electrode formed by impurity diffusion, the formed surface of the semiconductor substrate between the source electrode and the drain electrode and the lower electrode in a position other than the source electrode and the drain electrode
An OS oxide film is provided, and a mechanical quantity is detected by a current change between the source electrode and the drain electrode caused by displacement of the movable electrode. A part of a region of the movable electrode facing the LOCOS oxide film. A semiconductor dynamical quantity sensor, characterized in that it is configured to eliminate. 4. The region of the movable electrode facing the LOCOS oxide film is deleted so that the deleted area is larger than the undeleted area.
The semiconductor dynamic quantity sensor described. 5. The semiconductor dynamic quantity sensor according to claim 3, wherein a region of the movable electrode facing the LOCOS oxide film is deleted by forming an opening. 6. The semiconductor dynamic quantity sensor according to claim 3, wherein the region of the movable electrode facing the LOCOS oxide film is eliminated by narrowing the width.