JPH0614545B2 - Bidirectional thyristor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bidirectional thyristor generally called a triac, and more specifically, a bidirectional thyristor that achieves high sensitivity and high temperature characteristics at a high level. Regarding thyristors.

[Problems to be Solved by Prior Art and Invention]

Bidirectional thyristors (bidirectional reverse blocking three-terminal thyristors) or triacs are widely used in electronic circuits such as motor control circuits as switches for controlling alternating current.
The conventional bidirectional thyristor shown in FIGS. 8 to 11 has a first conductivity type (n type) first semiconductor region n ₁ (hereinafter, simply n ₁
Region) and a second conductive type (p-type) second semiconductor region p ₁ (hereinafter, simply referred to as “p ₁ type”) in contact with one side (lower side) of n _1.
p ₁ region) and a third semiconductor region p _{2 of} the second conductivity type (p type) (hereinafter, referred to as “p ₁ region”) that is in contact with the other side (upper side) of the n ₁ region.
(Hereinafter simply referred to as p ₂ region). The n ₁ region is composed of an n-type silicon semiconductor substrate which is a starting base material. Both the p ₁ region and the p ₂ region are formed by impurity diffusion and are arranged on the upper surface side of the substrate 1.
The p ₂ region is surrounded by the n ₁ region. p ₂ first conductivity type such that the surface is exposed in a region (n-type) fourth semiconductor region n ₂ (hereinafter, simply referred to as n ₂ region) and the fifth semiconductor region n ₄ (hereinafter, (Hereinafter referred to simply as n ₄ region) is formed by impurity diffusion. In the p ₁ region, there is a sixth of the first conductivity type (n type).
Semiconductor region n ₃ (hereinafter, simply referred to as “n ₃ region”) is formed by impurity diffusion. In the side surface region of the semiconductor substrate 1, a second
A conductive type (p-type) seventh semiconductor region p ₃ (hereinafter, simply referred to as p ₃ region) is formed by impurity diffusion. this
The p ₃ region is formed so as to be continuous with the p ₁ region by impurity diffusion from the upper surface and the lower surface in the state of the semiconductor wafer before element isolation.

As is apparent from FIG. 9, the planar shapes of the n ₁ region and the p ₂ region are substantially quadrangular. In the bidirectional thyristors shown in FIGS. 8 to 11, the n ₄ region is a bidirectional thyristor having a corner gate structure in which the n ₄ region is arranged close to one corner of the p ₂ region. The narrow region 2 of the p ₂ region is provided between the n ₂ region and the n ₄ region.
The patterns of the n ₂ region and the n ₄ region are determined so that

As is apparent from FIG. 11, the n ₃ region is formed in a part of the p ₁ region, and is arranged so as to have a portion which overlaps with the n ₄ region when seen in a plan view.

As is clear from FIGS. 8 and 10, the first main electrode T ₁ made of an aluminum electrode formed by vacuum deposition has a p
It is arranged so as to contact most of the _two regions and the n ₂ region. Ti (titanium) -Ni formed by vacuum deposition method or the like
The second main electrode T ₂ composed of a (nickel) electrode has a p ₁ region and an n
It is arranged so as to contact the _three areas. The gate electrode G made of an aluminum electrode formed by vacuum evaporation is
It is arranged so as to be in contact with most of the n ₄ region and part of the p ₂ region. The first main electrode T ₁ and the gate electrode G are in contact with each region through the opening of the SiO ₂ insulating film 3. In addition,
The first main electrode T ₁ is formed so as to short-circuit a part of the p ₂ region and the n ₂ region, and the gate electrode G is formed so as to short-circuit a part of the n ₄ region and the p ₂ region. ing.

The bidirectional thyristor has a first main electrode T ₁ and a second main electrode T ₂
Of positive and negative polarities of the first main electrode T of the gate electrode G
_The switching operation can be performed irrespective of the change in the positive or negative polarity of the voltage with respect to ₁ , that is, the gate voltage V _G. A second potential of the main electrode T ₂ with respect to the first main electrode T ₁ is positive, in the first mode the potential of the first gate electrode G with respect to the main electrode T ₁ is a positive, in FIG. 8 And the p ₁ region shown
The first thyristor portion 4 composed of the n ₁ region, the p ₂ region and the n ₂ region is electrically connected.

The first is positive and the second potential of the main electrode T ₂ with respect to the main electrodes T _1, in the second mode the potential of the gate electrode G to the first main electrode T ₁ is a negative first mode Similarly to the above, the first thyristor unit 4 becomes conductive.

A negative second potential of the main electrode T ₂ with respect to the first main electrode T ₁ is, in the third mode of the potential of the gate electrode G to the first main electrode T ₁ is a negative, and n ₃ region p ₁ region and n ₁
The second thyristor portion 5 including the region and the p ₂ region is electrically connected.

In the fourth mode in which the potential of the second main electrode T ₂ with respect to the _first main electrode T ₁ is negative and the potential of the gate electrode G with respect to the first main electrode T ₁ is positive, the third mode Similarly to, the second thyristor unit 5 becomes conductive.

As is clear from FIG. 8, the first and second thyristor sections 4 and 5 are equivalent to two antiparallel-connected thyristors. The portion 6 on the right side of FIG. 8 consisting of the n ₄ region, the p ₂ region, the n ₁ region, the p ₁ region and the n ₃ region is the first and second regions.
It is a portion used for conducting the thyristor portions 4 and 5 of.

By the way, in the bidirectional thyristor, one of the important issues is to improve the sensitivity, that is, how to make the first thyristor unit 4 or the second thyristor unit 5 conductive by the small gate trigger current I _GT . However, in the conventional bidirectional thyristors shown in FIGS. 8 to 11, this gate trigger current I _GT was not so small, and it was difficult to achieve high sensitivity.
That is, the gate trigger current I _GT is _composed of an active current component I _GTa that contributes to the conduction of the first thyristor unit 4 or the second thyristor unit 5, that is, a trigger, and a reactive current component I _GTb that does not contribute to the trigger. It is expressed as the sum of two current components. Therefore, in order to increase the sensitivity, it is necessary to reduce the reactive current component I _GTb that does not contribute to the trigger. For example, the conduction of the first thyristor portion 4 and the second thyristor portion 5 in the second mode and the third mode is the resistance (base resistance) R _{PB of} the p ₂ region sandwiched between the n ₁ region and the n ₄ region. by exceeding the diffusion potential of the pn junction product of the current flowing therethrough based upon a p ₂ region and the n ₄ region and, n ₄
It starts by injecting electrons from the region to the p ₂ region and then to the n ₁ region. Therefore, in the structural thyristor of FIGS. 8 to 11, the gate trigger current I _GT flowing in the p ₂ region below the n ₄ region becomes the effective current component I _{GTa and} becomes the gate electrodes G and p.
_The gate current I _GT flowing in the current path shown by the arrow 7 formed by the p ₂ region between the connecting portion A connecting to the ₂ region and the connecting portion B connecting the first main electrode T ₁ and the p ₂ region is the trigger described above. _{Becomes the} reactive current component I _GTb that does not contribute to Therefore, it is desirable to increase the short circuit resistance value R ₁ of this passage to reduce the reactive current component I _GT . However, in the bidirectional thyristor having the structure shown in FIGS. 8 to 11, it is difficult to increase the resistance value of the gate current passage indicated by the arrow 7 while electrically separating the n ₂ region and the n ₄ region.

In order to solve this problem, as shown in FIGS. 12 to 14, a structure in which the p ₂ region is left in the n ₄ region in an island shape and the gate electrode G is connected to the island portion 8 Bidirectional thyristors are being considered. In FIG. 13, the n ₄ region is shown thick because the thickness direction is greatly enlarged.
Since this thickness is significantly smaller than the lateral length of the n ₄ region, the resistance value from one end to the other end of the gate current path indicated by the arrow 9 is the lateral direction of the p ₂ region below the n ₄ region. It is almost decided by the resistance value of. n ₄ impurity concentration of p ₂ area under the area significantly lower than the impurity concentration of the surface of the p ₂ region. For example, the impurity concentration of the surface portion of the p ₂ region is on the order of 10 ¹⁷ to 10 ¹⁸ cm ^-3 , and the impurity concentration of the lower portion of the n ₄ region is 10 ¹⁵ to 1 1.
It is designed to the 0 ¹⁶ cm ^-3 order. According to the structure shown in FIGS. 12 and 13, only the passage indicated by the arrow 9 including the island-shaped p ₂ region serves as the current passage for the gate trigger current I _GT . Therefore, the gate trigger current I _GT becomes all the active current component I _GTa , and the reactive current component I _GTb almost disappears. Therefore, the gate trigger current I _GT can be reduced as compared with the structures shown in FIGS. 8 to 11. However, since the impurity concentration is low in the portion of the p ₂ region below the n ₄ region, the temperature dependence of the resistance of this portion (change in resistivity due to temperature change) becomes large. This is clear from FIG. 6 showing the relationship between the impurity concentration of the semiconductor and the resistivity. As a result, the temperature dependency of the gate trigger current I _GT (rate of change of current value due to temperature change) becomes large, and the temperature characteristic of the turn-on characteristic cannot be obtained well.

Therefore, the present invention solves the above problems, provides a bidirectional thyristor capable of reducing the gate trigger current I _GT to achieve high sensitivity and further reducing the temperature dependence of the gate trigger current. It is intended.

[Means for Solving the Problems]

The present invention for achieving the above-mentioned object is the first embodiment of the present invention.
Explaining with reference to the reference numerals of FIGS. 5 to 5, the first semiconductor region n ₁ of the first conductivity type and the second semiconductor region n ₁ of the second conductivity type adjacent to one side of the _first semiconductor region n ₁ Semiconductor region p ₁ and a third semiconductor region p _{2 of} the second conductivity type that is adjacent to the other side of the _first semiconductor region n ₁ and the third semiconductor region p 1 is provided. The region p ₂ has fourth and fifth semiconductor regions of the first conductivity type which are adjacent to the third semiconductor region p ₂ and have a portion exposed on the surface of the semiconductor substrate 1.
n ₂ and n ₄ are formed, and the second semiconductor region p ₁ has a portion exposed on the surface of the semiconductor substrate 1 and is adjacent to the second semiconductor region p ₁ . A conductive type sixth semiconductor region n ₃ is formed, and the sixth semiconductor region n ₃ is formed.
n ₃ has a portion which overlaps with the fifth semiconductor region n ₄ when seen in a plan view, and the surfaces of the third and fourth semiconductor regions p ₂ and n _{2 form} the first main electrode T ₁ . The surfaces of the third and fifth semiconductor regions p ₂ and n ₄ are in contact with the gate electrode G, and the surfaces of the second and sixth semiconductor regions p ₁ and n ₃ are in contact with each other.
In the bidirectional thyristor formed in contact with the main electrode T ₂ of
An island shape or a notch shape in which the third semiconductor region p ₂ penetrates into the fifth semiconductor region n ₄ so as to penetrate from the one main surface of the fifth semiconductor region n _{4 to} the other main surface. Of the penetrating portion 8 or 8a, the penetrating portion 8 or 8a is exposed on the surface of the semiconductor substrate 1, and the gate electrode G is located in the penetrating portion 8 or 8 with respect to the third semiconductor region p ₂ . 8a
And the first main electrode T ₁ and the gate electrode G are connected via a resistor 12 made of polycrystalline silicon having a negative temperature coefficient. Related to.

[Work]

According to the present invention, the gate trigger current I _GT flows by being divided into the third semiconductor region p ₂ including the penetration portion 8 or 8a and the resistor 12. The resistivity of the third semiconductor region p ₂ has a characteristic of increasing with temperature rise, and the resistivity of the resistor 12 made of polycrystalline silicon has a characteristic of decreasing with temperature rise. Therefore, the gate trigger current I _GTb flowing in the third semiconductor region p ₂ decreases as the temperature rises, and the resistor 12
The gate trigger current I _GTa flowing in the gate current increases as the temperature rises. Therefore, the temperature dependences of the gate trigger currents I _GTa and I _GTb are mutually compensated, and the gate trigger current I _GT (I
The temperature dependency of _GT = I _GTa + I _GTb ) can be reduced. Further, the gate trigger current I _GTa flowing through the resistor 12 made of polycrystalline silicon is a reactive current component that does not contribute to the trigger, but since the resistor 12 has a relatively large resistance value, the gate trigger current I _GTa can be reduced. Further, the gate trigger current I _GTb flows into the third semiconductor region p ₂ below the fifth semiconductor region n ₄ , so that it effectively acts on the trigger. Therefore, the gate trigger current I _GT is relatively small, and a highly sensitive bidirectional thyristor can be provided.

〔Example〕

Next, a bidirectional thyristor (triac) according to an embodiment of the present invention will be described with reference to FIGS. However, in FIGS. 1 to 5, substantially the same parts as those in FIGS. 8 to 14 are designated by the same reference numerals, and the description thereof will be omitted.

The bidirectional thyristor shown in FIG. 1 to FIG. 5 has a resistor 12 made of polycrystalline silicon (polysilicon).
12 to 14 except that the main electrode T ₁ and the gate electrode G are connected to each other and the shapes of the first main electrode T ₁ and the gate electrode G are partially changed accordingly. Are identically configured. In the n ₄ region (fifth semiconductor region) of this embodiment, an island-shaped intrusion portion 8 of the p ₂ region is provided as is clear from FIG. As shown in FIG. 1, the island-shaped penetration portion 8 has a through hole 11 formed in the n ₄ region.
A part of the p ₂ region (third semiconductor region) invaded. This island-shaped intrusion portion 8 is formed by impurity diffusion in the p ₂ region.
It is obtained by forming the n ₄ region in a ring shape. In addition,
The island-shaped penetration portion 8 is formed so as to penetrate from one main surface of the n ₄ region to the other main surface.

An insulating film 3 made of a silicon oxide film formed by thermal oxidation is provided on the upper surface of the semiconductor substrate 1. Two openings 3a and 3b are formed in the insulating film 3 as shown in FIG. 3, and the n ₂ region and the p ₂ region are in contact with the _first main electrode T ₁ through the opening 3a, and the n ₄ region The island-shaped intrusion portion 8 is in contact with the gate electrode G through the opening 3b. The resistor 12 is formed above the narrow region 2 of the p ₂ region located between the n ₂ region and the n ₄ region with the insulating film 3 interposed therebetween. The resistor 12 is made of polysilicon and is well known in the CVD method (Chem.
ical vapor deposition). In this embodiment, first, the insulating film 3 is formed on the front surface of the upper surface of the semiconductor substrate 1, and then the polysilicon layer is formed on the entire upper surface of the insulating film 3. The polysilicon layer is selectively etched so that the resistor 12 remains. Next, after the openings 3a and 3b are provided in the insulating film 3 by etching, the first main electrode T ₁ and the gate electrode G, which are AI electrodes, are formed. As is apparent from FIG. 3, the insulating film 3 formed above the narrow region 2 extends to the inside of the n ₂ region and the n ₄ region in plan view. As shown in FIG. 4, the resistance region 12 is formed so as to overlap a part of the narrow region 2 in plan view. As is apparent from FIGS. 1 and 4, the first main electrode T ₁ and the gate electrode G extend above the resistor 12, and both electrodes are electrically connected via the low antibody 12. . Therefore, the resistor 12 acts as a current path having a relatively large resistance value of the gate trigger current.

The bidirectional thyristor of this embodiment has the following effects.

(1) Since the gate trigger current I _GT flows in a divided manner in the resistor 12, the temperature dependence of the gate trigger current I _GTb (active current component) flowing in the p ₂ region including the island-shaped intrusion portion 8 can be reduced, resulting in As a result, the temperature dependence of the gate trigger current I _GT can be reduced. That is, the first main electrode T ₁ and the gate electrode G are electrically connected via the resistor 12. Therefore, the gate trigger current I _GT splits into a passage indicated by the arrow 9 including the island-shaped intrusion portion 8 and a passage indicated by the arrow 7 passing through the low antibody 12. Here, as shown in FIG. 7, the low antibody 12 made of polysilicon has a negative temperature coefficient in which the resistance value decreases as the temperature rises in the temperature range where the bidirectional thyristor is normally used. The temperature coefficient is opposite to that of the semiconductor shown in FIG. Therefore, when the temperature of the bidirectional thyristor rises due to the increase of the self-heating temperature and the rise of the ambient temperature, the gate trigger electrode I _GTb flowing through the passage shown by the arrow 9 decreases and the gate trigger current I _GT flowing through the passage shown by the arrow 7 decreases. _GTa will increase. Further, the resistance value of the resistor 12 can be arbitrarily set by changing its sheet resistance and shape (width, length, layer thickness, etc.). Therefore, the resistor 12
The temperature dependence of the gate trigger current I _GTb can be compensated for by the gate trigger current I _GTa by setting the resistance value of 1 to a resistance value that can effectively compensate the temperature dependence of the gate trigger current I _GTb . The resistor 1 made of polysilicon is used.
The sheet resistance of 2 can be arbitrarily set according to the amount of ion implantation and the condition of heat treatment after implantation.

(2) Since the resistor 12 made of polysilicon can be set to any resistance value, a highly sensitive bidirectional thyristor with a small gate trigger current I _GT can be realized. That is, the gate trigger current I _GTa flowing through the resistor 12 is a reactive current component that does not contribute to the trigger. However, since the resistor 12 can have a relatively large resistance value, the reactive current component is
It can be made sufficiently smaller than that of the bidirectional thyristor shown in FIGS. Further, the gate trigger current I _GTb flowing through the passage indicated by the arrow 9 is all an effective current component contributing to the trigger. Therefore, as compared with the bidirectional thyristors shown in FIGS. 12 to 14, the gate trigger current increases by the reactive current component, but this is not a level that poses a practical problem, and it is better than the bidirectional thyristors shown in FIGS. 8 to 11. It is possible to provide a highly sensitive bidirectional thyristor having a sufficiently small gate trigger current I _GT .

[Modification]

The present invention is not limited to the above-mentioned embodiments, and the following modifications are possible, for example.

(1) According to the present invention, the temperature dependency of the gate trigger current is improved not only in the second and third modes in which the gate electrode G is negative, but also in the first and fourth modes in which the gate electrode G is positive. . Therefore, it is more effective if the gate electrode G is combined with a bidirectional thyristor having improved positive mode I _GT by devising the shapes of the n ₂ region and the first main electrode T ₁ . In order for the gate electrode G to improve the positive mode I _GT , for example, as shown in FIG. 15, the protrusion 13 in the n ₂ region is extended along the edge of the _first main electrode T ₁ indicated by the broken line. Let n ₄ be a ring n on the left side of the area
_Two regions can be formed.

(2) As shown in FIGS. 16 and 17, a cut-in intrusion 8a may be provided in the n ₄ region. At this time, most of the cut-in penetration portion 8a in the p ₂ region is covered with the insulating film 3, and only the inner portion of the cut-in penetration portion 8a is brought into contact with the gate electrode G. In this case, the gate trigger current passes through the resistor 12 in the first passage, the second passage formed by the notch-like intrusion portion 8a and the surface of the narrow portion 2 in the p ₂ region, and the p passage below the n ₄ region. It flows dividedly into a third passage that passes through _two regions. This FIG. 16 and FIG.
In the bidirectional thyristor shown, the gate trigger current flowing through the first and second passages becomes a reactive current component that does not contribute to the trigger. However, the second passage has a notch-like penetration 8
Since a is formed and the passage length is long, most of the current flowing through the semiconductor substrate mainly flows through the third passage. Further, the passage length is set such that the resistance of the second passage is larger than the resistance of the first passage. Therefore, the reactive current component does not increase significantly. However,
All gate trigger currents flowing in the p ₂ region are below the n ₂ region.
The structure of the embodiment is more preferable because it becomes an effective current component flowing in the p ₂ region and high sensitivity can be achieved at a high level.

(3) Since the sheet resistance of polysilicon can be arbitrarily set as described above, the shape of the resistor 12 can be variously modified. For example, the width of the resistor 12 (the length in the direction in which the narrow region 2 extends) may be increased. However, as shown in FIG. 3, the vicinity of the end of the protrusion 13 _{serves as} a main current path for the gate trigger current I _GTb , and it is considered undesirable to form the resistor 12 above this.
Therefore, it is desirable that the resistor 12 is formed above the narrow region 12 so as not to extend outside the protrusion 13 in plan view.

(4) A channel stopper or a field plate may be formed on a part of the surface of the p ₂ region and the p ₃ region.

(5) It is also effective for a bidirectional thyristor (side gate type bidirectional thyristor or center gate type bidirectional thyristor) of a type in which n ₄ (gate region) is formed in a region other than near the corner of the p ₂ region.

(6) The first main electrode T ₁ and the gate electrode G can be formed of polysilicon.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a bidirectional thyristor in which the temperature dependence of the gate trigger current is small and the sensitivity is relatively high.

[Brief description of drawings]

FIG. 1 is a sectional view showing a bidirectional thyristor according to an embodiment of the present invention by cutting along the line corresponding to the line II in FIGS. 2, 3, and 5, and FIG. 2 is an embodiment. 3 is a plan view showing a surface of a semiconductor substrate of the thyristor, FIG. 3 is a plan view showing a state before a resistor and an electrode are provided, FIG. 4 is a plan view showing a gate electrode and its vicinity, and FIG. FIG. 6 is a temperature characteristic diagram showing the relationship between the temperature of silicon and the resistivity, FIG. 7 is a temperature characteristic diagram showing the relationship between the temperature of polysilicon and the sheet resistance, and FIG. The figure shows a conventional bidirectional thyristor.
9, 10, and 11 are sectional views of a portion corresponding to the line VIII-VIII, FIG. 9 is a plan view showing the surface of the semiconductor substrate of the bidirectional thyristor of FIG. 8, and FIG. 8 is a plan view of the bidirectional thyristor, FIG. 11 is a sectional view of a portion corresponding to the line XI-XI in FIG. 8, FIG. 12 is a plan view showing another conventional bidirectional thyristor, and FIG. 12 and 14 are sectional views of a portion corresponding to line XIII-XIII, FIG. 14 is a sectional view of a portion corresponding to XIV-XIV of FIG. 13, and FIG. 15 is both a modification of the present invention. FIG. 16 is a plan view showing the surface of the semiconductor substrate of the bidirectional thyristor, and FIG. 16 shows a bidirectional thyristor n _{4 according to} another modification of the present invention.
FIG. 17 is a plan view showing the region and the surface of the semiconductor substrate in the vicinity thereof, and FIG. 17 is a plan view showing the gate electrode of the bidirectional thyristor of FIG. 16 and the vicinity thereof. 8 ...... islands penetration portion, 12 ...... resistors, T ₁ ...... first main electrode, T ₂ ...... the second main electrode, G ...... gate electrode, n ₁
...... First semiconductor region, p ₁・ ・ ・ Second semiconductor region, p ₂・ ・ ・
… Third semiconductor region, n ₂ …… Fourth semiconductor region, n ₄ ……
Fifth semiconductor region, n ₃ ... Sixth semiconductor region.

Claims (1)

[Claims] 1. A first semiconductor region of a first conductivity type (n _1), second semiconductor region (p of one second conductivity type adjacent to the side of said first semiconductor region (n _{1) 1} ) and the first semiconductor region (n
₁ ) A third semiconductor region of the second conductivity type adjacent to the other side
(p ₂ ) and a semiconductor substrate (1) having
Fourth and fifth in the semiconductor region (p ₂₎ of the semiconductor body first conductivity type which is adjacent to the have a portion exposed to the surface of (1) third semiconductor region (p ₂₎ Semiconductor region (n ₂ ) (n ₄ )
Is formed, and the second semiconductor region (p ₁ ) has a portion exposed on the surface of the semiconductor substrate (1).
Semiconductor region (p ₁₎ of the first conductivity type which is adjacent to the sixth semiconductor region (n ₃₎ are formed, the semiconductor region (n ₃₎ of the sixth when viewed in a plan view The fifth semiconductor region (n ₄ )
Has a portion overlapping with the third and fourth semiconductor regions (p
The surface of ₂ ) (n ₂ ) is in contact with the first main electrode (T ₁ ), and the surfaces of the third and fifth semiconductor regions (p ₂ ) (n ₄ ) are gate electrodes.
Is in contact with (G), and the second and sixth semiconductor regions (p ₁ )
In the bidirectional thyristor in which the surface of (n ₃ ) is in contact with the second main electrode (T ₂ ), the third semiconductor region (p ₂ ) is the fifth semiconductor region (n ₄ ).
The fifth part is formed so as to penetrate from one main surface to the other main surface.
Has an island-like or notch-like intrusion part (8 or 8a) penetrating into the semiconductor region (n ₄ ) of the above, and the intrusion part (8 or 8a) is exposed on the surface of the semiconductor substrate (1). The gate electrode (G) is in contact with the third semiconductor region (p ₂ ) at the penetrating portion (8 or 8a), and the first main electrode (T ₁ ) and the gate electrode A bidirectional thyristor characterized by being connected to (G) via a low antibody (12) made of polycrystalline silicon having a negative temperature coefficient.