JPH06275634A - Power transistor device - Google Patents

Abstract

PURPOSE:To keep a Zener voltage constant in a wide range of temperature change, by forming a Zener diode wherein a plurality of p-r junctions are arranged on a poly-silicon film. CONSTITUTION:A Zener diode Z is formed between a common collector C of a driver transistor T2 and a power transistor T1 and the base of the driver transistor T2. In the Zener diode Z, a plurality of p-n junctions 22 are formed on a poly-silicon film so as to be connected in series. The Zener diode serves as a voltage clamping means for clamping a counter-electromotive force in a primary side coil connected with the collector. Hence the temperature characteristics coefficient of a Zener diode becomes very small, and the counter- electromotive force generated in an inductive load can be set as a stable voltage independently of temperature change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transistor device, and more particularly to a so-called IC in an internal combustion engine ignition device.
It is related to effective technology for igniters.

[0002]

2. Description of the Related Art Conventionally, 1 is applied to each cylinder between a collector and a base of a bipolar transistor which constitutes a power transistor device used in an ignition device (IC igniter) of a multi-cylinder internal combustion engine mounted on an automobile. A Zener diode is provided to stabilize the electromotive force of the secondary coil. The Zener voltage of the Zener diode stabilizes the counter electromotive voltage generated in the primary coil. As a power transistor device as described above,
A Darlington transistor circuit is used. Japanese Patent Publication No. 2-51256 discloses a power transistor device using a Darlington transistor circuit.

[0003]

In the above power transistor device, the Zener diode provided between the collector and the base is a pn in the silicon bulk.
It was formed using joining. Therefore, the Zener voltage of the Zener diode is determined by the concentration and depth of the pn junction in the silicon bulk, and the temperature characteristic of the Zener voltage in the Zener diode has a positive temperature characteristic coefficient (usually about 1000 to 2000 ppm / ° C). have. Therefore, it has been clarified by the inventor of the present application that the Zener voltage rises as the ambient temperature of the power transistor device rises.

For example, when the Zener voltage of the Zener diode increases, the counter electromotive voltage of the primary coil increases correspondingly, so that the output voltage from the secondary coil applied to each cylinder increases. As an example, assume that the temperature characteristic of the silicon bulk is 1500 ppm / ° C., the Zener voltage is 370 V, and the output voltage of the secondary coil is 50,000 V when the atmosphere of the power transistor is −40 ° C. To do. When the atmosphere of the power transistor device rises to 140 ° C. under this condition, the Zener voltage rises to about 470V, and accordingly, the output voltage of the secondary coil exceeds 60,000V. Conventionally, a cable having a sufficient withstand voltage that allows for the above voltage fluctuation was used as the cable for the secondary coil, but the withstand voltage of the cable used for cost reduction and weight reduction. It has been clarified by the inventor of the present application that when the voltage is reduced, the output voltage at the time of voltage fluctuation becomes higher than the withstand voltage and the cable for the secondary coil may be broken.

An object of the present invention is to provide a power transistor device having a collector voltage clamping function which is stable against temperature changes. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0006]

The outline of a typical one of the inventions disclosed in the present application will be briefly described as follows. That is, in a transistor in which a collector is connected to an inductive load and a switch current flows, a Zener diode having a plurality of pn junction structures formed in series in a polysilicon film is provided between the collector and the base. . A MOSFET that is switch-controlled by a control voltage formed based on the Zener current flowing through the Zener diode is provided to form a current path in parallel with the Zener diode.

[0007]

According to the above-mentioned means, since the Zener diode formed in the polysilicon film has a very small temperature characteristic coefficient, the back electromotive force generated in the inductive load is stable regardless of temperature change. Can be set to voltage. By providing the MOSFETs in parallel, the relatively large on-resistance value of the Zener diode can be reduced.

[0008]

FIG. 3 is a circuit diagram of an embodiment of the power transistor device according to the present invention. The power transistor device of this embodiment is configured to be used in a so-called IC igniter, and is incorporated in a single IC pellet. That is, this power transistor device is formed on a single semiconductor substrate such as single crystal silicon by a known semiconductor integrated circuit manufacturing technique.

In the power transistor device 1, its collector connection terminal C is connected to one end of the primary coil 2, its base connection terminal B is connected to the pickup device 3, and its emitter connection terminal E is the ground potential of the circuit ( Ground). A battery voltage from the battery 4 is applied to the other end of the primary coil 2. A secondary side coil 5 is provided which is electromagnetically coupled to the primary side coil 2, and the primary side voltage is boosted in proportion to the winding ratio of the primary side coil and the secondary side coil. It is output from the side coil 5. The output voltage of the secondary coil 5 is supplied to the spark plug 6.

The power transistor device comprises a driver transistor T ₂ as an input side in the Darlington configuration.
And the power transistor T ₁ on the output side is used as a switching element. A common collector C of the driver transistor T ₂ and the power transistor T _1.
And the base B of the driver transistor T ₂ between
A Zener diode Z using a pn junction structure formed in a polysilicon film, which will be described later, is provided as voltage clamping means for clamping the counter electromotive voltage in the primary coil connected to the collector. Transistor T ₂
A resistor R ₂ between the base and the emitter of the transistor T ₁
A resistor R ₁ is provided between the base and the emitter of each.

FIG. 1 is a sectional view of the element structure of an embodiment of the power transistor device according to the present invention.
The power transistor device 1 is formed on a silicon substrate (hereinafter referred to as a substrate) 10 as an n-conductivity type semiconductor. In this substrate 10, two p-conductivity-type first base regions 11a and second base regions 11b of the two transistors T ₁ and T ₂ are diffused from the first main surface. The first base region 11a and the second base region 11b together with the substrate 10 include the first pn junction 12a and the second pn junction 12a.
Each pn junction 12b is formed.

In these first base region 11a and second base region 11b, n-conductivity type emitter regions 9a and 9b of _two transistors T ₁ and T ₂ are diffused from the same first main surface. . An oxide film 13 as an inactive layer is formed on the first main surface of the substratum 10.
However, each pn junction on the first main surface is selectively formed so as to cover the region exposed on the surface.

Emitter region 9 of power transistor T ₁
An emitter electrode 9 is formed on a by depositing a conductive metal material such as aluminum. The emitter connection terminal E of the power transistor device 1 is connected to the emitter electrode 9.

Base region 1 of driver transistor T ₂
A base electrode 8 is formed on 1b by depositing a conductive metal material such as aluminum. The power transistor device 1 is provided on the base electrode 8.
The base connection terminal B in is connected.

A collector electrode 7 is formed on the second main surface of the substrate 10 by depositing a conductive metal material such as Ag. In this collector electrode 7,
The collector connection terminal C of this power transistor device 1 is connected. The wiring means 24 in which the base of the transistor T ₁ and the emitter of the transistor T ₂ are coated with a conductive metal material such as aluminum.
Are electrically coupled to each other via.

Base region 1 of driver transistor T ₂
On the region of the oxide film 13 formed on 1b, the Zener diode Z is formed by the pn junction structure formed in the polysilicon film. A pn junction structure using this polysilicon film will be described below with reference to the manufacturing process chart shown in FIG.

FIG. 4 is a manufacturing process diagram of an embodiment of the Zener diode Z used in the power transistor device 1 according to the present invention.

As shown in FIG. 4A, a polysilicon film 20 is selectively deposited on the oxide film 13 formed on the surface of the base region 11b of the driver transistor T ₂ by the CVD method or the like. It

As shown in FIG. 4B, boron (B) as a p-conductivity type impurity is implanted into the polysilicon film 20 by an appropriate means such as an ion implantation method to form a polysilicon film. A p-conductivity type region is formed at 20.

As shown in FIG. 4C, a mask 21 made of a resist is formed by lithography on the polysilicon film 20 that has become the p-conductivity type region. Then, phosphorus (P) as an n-conductivity type impurity is selectively introduced into the polysilicon film 20 through the mask 21 by means such as an ion implantation method. This allows
A plurality of pn junctions 22 are formed in series on the polysilicon film 20. In the figure, for the sake of convenience, a p-conductivity type region and n
Although only four conductivity type regions are illustrated in total, the breakdown voltage of the pn junction 22 determines a Zener voltage Vz described later. Therefore, the number of the pn junctions 22 is large corresponding to the desired Zener voltage Vz. It will be provided.

As shown in FIG. 4D, a protective oxide film 14 is formed on the polysilicon film 20 having a plurality of pn junctions 22 formed thereon.

In the Zener diode Z having the plurality of pn junctions 22 formed on the polysilicon film 20 manufactured as described above, the p-conductivity type region at one end of the pn junction 22 group is electrically connected to the base electrode 8. Connected to the pn junction 22
The n-conductivity type region at the other end of the group has a second main surface of the substrate 10 via a contact part CON with the wiring means 23 and the substrate 10 which is coated with a conductive metal material such as aluminum. That is, the collector electrode 7
Electrically connected to.

In the circuit diagram of FIG. 3, resistors R ₁ and R ₂ provided between the bases and emitters of the transistors T ₁ and T ₂ , respectively, are formed on the substrate 10 of FIG. Is omitted in.

FIG. 2 shows a layout diagram of an embodiment of the power transistor device 1 according to the present invention.
In the figure, the thick shaded portion is an oxide film, and the thin shaded portion is formed of a conductive metal material such as aluminum. The thick frame portion is an electrode. A portion surrounded by a dotted line is a portion formed under the oxide film or the metal material, and shows a portion which cannot be directly seen from the upper portion of the device 1. It is to be noted that FIG. 1 is a drawing showing a cross-sectional structure taken along one-dot chain line AA ′ in the drawing.

On the right side of the chip is a power transistor T ₁
Is formed, and the base electrode 8 of the driver transistor T ₂ is formed on the left side of the chip.
The Zener diode Z is substantially below the base electrode 8 of the driver transistor T ₂ , and is substantially formed on a base region (not shown) on the chip.

The p-conductivity type region at one end forming the anode electrode of the Zener diode Z is not particularly limited, but the n-conductivity type region at one end connected to the base electrode 8 from the side and forming the cathode electrode is made of a metal material. It is connected to the substrate acting as the collector region of the transistors T ₁ and T ₂ through the wiring means 23 and the contact portion CON formed by the above.

Although not particularly limited, the current supplied to the base connection terminal B of the power transistor device 1 is optimized by a computer or the like based on the ignition signal detected by the pickup device 3 provided in the distributor. Controlled by timing.

In this embodiment, a Zener diode is constructed by using a pn junction formed in a polysilicon film. The Zener diode formed by using the polysilicon film is so small that its temperature characteristic coefficient (ppm / ° C.) becomes almost zero. Therefore,
The voltage Vs of the primary coil 2 in a wide temperature range from a low temperature such as −40 ° C. to a high temperature such as + 140 ° C.
Can be kept almost constant.

In response to this, the output voltage Vp formed in proportion to the winding ratio of the primary side coil 2 and the secondary side coil 5 is also made a stable high voltage. Therefore, a stable spark voltage can be obtained over a wide temperature range as described above. As a result, the withstand voltage of the cable that guides the output voltage Vp to the ignition coil can be minimized, and the cost and weight can be reduced.

When a Zener diode using a diffusion layer is used as in the prior art, the temperature characteristic thereof allows the Zener voltage to be sufficient to obtain a sufficient primary coil voltage even at a low temperature such as -40 ° C. When Vz is set to about 350V, it becomes too high at 440V or higher at a high temperature such as + 140 ° C., and the dielectric strength of the cable connected to the secondary coil 5 becomes a problem. Therefore, it is necessary to form an electric path including a cable so as to guide the voltage Vp of the secondary coil to the ignition plug so as to have a sufficient withstand voltage in consideration of the temperature characteristics as described above.

FIG. 5 shows a circuit diagram of another embodiment of the power transistor device according to the present invention. In the above embodiment, the Zener diode Z is formed by using the pn junction formed in the polysilicon film as the voltage clamping means.
Was to be composed. In this case, since the on-resistance value is relatively large, for example, 300Ω, when the current value of the breakdown current flowing through the Zener diode Z due to the counter electromotive voltage Vs is large or the current value fluctuates, the resistance component causes 1 The clamp voltage Vs of the secondary coil will change.

Therefore, in this embodiment, the diode D1 is connected to the Zener diode Z, and its voltage is changed to MO.
Supply to the gate and source of SFETQ, MOSFETQ
Source and drain are connected to the base and collector of the transistor T ₂ , respectively. In other words, the MOSFET Q having a small ON resistance forms a current path in parallel with the Zener diode Z having a large ON resistance. A resistor R ₃ is provided between the gate and the source of the MOSFET Q.

Although not particularly limited, the diode D1 is
A pn junction formed in the polysilicon film is used. Similarly, the resistor R _{3 is} also formed by introducing an appropriate impurity into the polysilicon film.

FIG. 6 shows a layout diagram of an embodiment of the power transistor device of FIG. Since the basic structure is the same as that of the embodiment shown in FIG. 2, only the difference will be described. Although not particularly limited, in addition to the Zener diode Z using a polysilicon film on the base bonding pad which constitutes the gate connection electrode B of the driver transistor T ₂ and on the gate region, a region close to the Zener diode Z is provided. A MOSFET Q, a diode D1 connected between the gate and the source thereof, and a diode D2 connected between the source and the drain of the MOSFET Q are formed. As described above, since the Zener diode Z, the diodes D1 and D2, and the MOSFET Q are arranged under the base bonding that forms the base connection electrode B of the driver transistor T ₂ , the substantial chip size of the power transistor device is reduced. It is possible to configure the device without increasing the size.

In the drawing, a portion surrounded by a thick diagonal line shows an oxide film, and a portion surrounded by a dotted line shows a wiring means made of aluminum or the like, or a portion hidden under an electrode. Moreover, what is shown by the one-dot chain line shows the connection relationship between the elements. The two-dot chain line A in the figure
A cross-sectional view of the device structure taken along the line indicated by -A 'is shown in FIG. 7 described below.

FIG. 7 is a sectional view of the element structure of one embodiment when the power transistor device 1 of FIG. 6 is cut along the chain double-dashed line AA '. The MOSFET Q uses an n-conductivity type substrate as a drain region. As a result, the collector regions of the transistors T ₁ and T ₂ and the drain region of the MOSFET Q are integrally configured and electrically connected to the collector connection terminal C connected to the primary coil 2.

The channel region of the MOSFET Q is a p-conductivity type p formed on the n ^- conductivity type substrate.
_{It is} composed of _two areas 31. An n-conductivity type n ₂ region 32 is formed in the p ₂ region 31 and is used as a source region. A gate electrode 33 is formed on the channel region 31 sandwiched between the source region 32 and the substrate via a thin gate insulating film. Source area 3
The base electrode 8 of the transistor T ₂ extends and is connected to 2.

Although not particularly limited, the region where the MOSFET Q is formed is surrounded by the p ₁ region electrically connected to the base region of the transistor T ₂ so as not to be influenced by the parasitic transistor. .

FIG. 8 shows a sectional view of the element structure of the Zener diode Z corresponding to the embodiment circuit of FIG.
The n-conductivity type region on one end side which acts as the cathode electrode of the Zener diode is an n-conductivity type n ₁ region for ohmic contact provided on the first main surface of the substrate and an appropriate conductivity such as an aluminum layer. They are connected by the wiring means 23 made of the metal material. The ohmic contact region n ₁ is a semiconductor region that is formed at the same time as the emitter regions of the transistors T ₁ and T ₂ shown in FIG.
Is shown as a contact CON in the layout of FIG.

The p-conductivity type region on the other end side which acts as the anode electrode of the Zener diode Z is connected to the gate electrode 33 of the MOSFET Q by a wiring means made of a suitable conductive metal material such as an aluminum layer. It The manufacturing method of the Zener diode Z of this embodiment is as follows.
Since it is the same as the embodiment of FIG. 4, the description thereof will be omitted.

In the embodiment shown in FIG. 5, the Zener diode Z is caused by the counter electromotive voltage generated in the primary coil 2 when the transistors T ₂ and T ₁ are turned off by the pickup device 3. When a breakdown occurs, a break current flows through the diode D, and the voltage causes the MOSFET Q to turn on. As a result, the counter electromotive voltage generated in the primary coil 2 has a voltage clamping action due to the current flowing through both the Zener diode Z and the MOSFET Q, so that the Zener diode Z has a relatively large on-resistance such as 300Ω. However, the on-resistance of MOSFETQ is, for example, 1
Since it is as small as 00Ω, the overall on resistance is 75Ω.
Can be made smaller. As a result, the voltage Vs of the primary coil 2 can be stabilized in correspondence with a desired Zener voltage by minimizing the influence of the on-resistance of the Zener diode. In response, 2
The boosted output voltage Vp generated in the secondary coil 5 can also be stabilized.

FIG. 9 is a block diagram of an ignition device system for controlling the ignition timing of a multi-cylinder internal combustion engine of an automobile or the like by using a plurality of the power transistor devices of FIG. 3 or 5.

In FIG. 9, n power transistor devices are used, and although not particularly limited, an n-cylinder internal combustion engine is controlled using n power transistor devices. 1
1 to 1n are the power transistor devices of FIG. 3 or FIG. The collector terminals C of the power transistor devices 11 and 1n are connected to the battery 4 via the primary side coils 21 and 2n and the switch SW.

The emitter terminals E of the power transistor devices 11 to 1n are grounded to the ground level. The base terminals B of the power transistor devices 11 to 1n are connected to the engine control unit ECN composed of a microcomputer or the like. The engine control unit ECN uses the power transistor devices 11 to 11 at predetermined timings based on information such as the engine speed.
A signal of a predetermined level is sequentially output to the 1n base terminal B. The switch SW is a switch for controlling the on / off of the engine.

For example, when the present system is applied to an internal combustion engine having a built-in 6-cylinder engine, 6 power transistor devices are required. In addition, the power transistor device 11
1 to 1n need not be formed in separate substrates, and are not particularly limited, but they may be formed in a number of substrates less than n or even in one substrate.

The resistor R ₃ provided in parallel with the diode D1 is provided for absorbing a disturbance surge. The diode D2 provided between the drain and the source of the MOSFET Q is a parasitic diode generated from the semiconductor structure. This means that the diode D3 between the collector and the emitter of the transistors T ₁ and T ₂ is a similar parasitic diode.

The operation and effect obtained from the above embodiment are as follows. That is, (1) In a power transistor device, a plurality of pn junctions are arranged side by side in a polysilicon film to form a Zener diode, so that a temperature characteristic coefficient of p is extremely small.
Since the breakdown voltage characteristic of the n-junction can be utilized as the Zener voltage, the effect that the Zener voltage can be maintained constant regardless of the temperature change in a wide range is obtained.

(2) By using the power transistor device equipped with the Zener diode of the above (1) in the IC igniter, the primary side voltage can be set to the predetermined voltage even in the engine room which varies widely from low temperature to high temperature. Since it can be maintained, the boosted secondary voltage can also be stably operated, and the ignition operation of the engine can be stably maintained. As a result, the withstand voltage of the cable that connects the secondary coil and the spark plug can be set to the required minimum, so that the cost and weight can be reduced.

(3) By forming a polysilicon film on the first main surface of the substrate and forming a pn junction group, the structure and the manufacturing process are simplified, so that the productivity can be improved. The effect is obtained.

(4) Since the Zener voltage of the Zener diode can be set by the number of p-junctions formed in the polysilicon film, it is easy to set the Zener voltage to a desired voltage value. can get.

(5) By forming a MOSFET and performing switch control by a voltage signal formed based on the Zener current of the Zener diode, and forming a current path in parallel with the Zener diode, a relatively large on-resistance can be obtained. Even if the Zener diode included therein is used, it is possible to obtain the effect that the counter electromotive voltage in the inductive load can be stably clamped.

(6) According to the above (5), when the IC igniter is used, the primary side voltage can be maintained at the predetermined voltage even in the engine room that changes in a wide range from low temperature to high temperature. The secondary side voltage can also be stably operated, and the ignition operation of the engine can be stably maintained. As a result, the withstand voltage of the cable that connects the secondary coil and the spark plug can be set to the required minimum, so that the cost and weight can be reduced.

(7) By arranging the MOSFET under the base bonding pad of the driver transistor T ₂ , it is possible to obtain the effect that the stable voltage clamping operation can be performed without increasing the chip size of the power transistor device. To be

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention of the present application is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the arrangement of the Tze diode Z formed in the polysilicon film is
In addition to those formed under the base electrode, various embodiments such as forming so as to extend across the junction between the base and the collector can be adopted. The transistor may be a Darlington type transistor, and the other driver transistor T ₂ on the input side may be omitted to form another transistor circuit like a power transistor.

In the above description, the case where the invention made by the present inventor is mainly applied to the IC igniter which is the field of application which is the background of the invention has been described. However, the invention is not limited to this, and an inductive load is driven. It can be widely used as a power transistor device.

[0056]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows. That is, in the power transistor device, by forming a plurality of pn junctions in a polysilicon film side by side to form a Zener diode, the breakdown voltage characteristics of the pn junction having an extremely small temperature coefficient can be utilized as the Zener voltage. It is possible to keep the Zener voltage constant regardless of a wide temperature change. Even if a Zener diode having a relatively large on-resistance is used, the inductive load is formed by switching the MOSFET with a voltage signal formed based on the Zener current of the Zener diode and forming a current path in parallel with the Zener diode. The counter electromotive voltage in can be stably clamped.

[Brief description of drawings]

FIG. 1 is a sectional view of an element structure showing an embodiment of a power transistor device according to the present invention.

FIG. 2 is a layout diagram showing an embodiment of a power transistor device according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment of a power transistor device according to the present invention.

FIG. 4 is a manufacturing process diagram for describing the manufacturing method of the Zener diode used in the power transistor device according to the present invention.

FIG. 5 is a circuit diagram showing another embodiment of the power transistor device according to the present invention.

FIG. 6 is a layout diagram showing an embodiment of the power transistor device of FIG.

7 is a cross-sectional view of an element structure showing an embodiment of the power transistor device of FIG.

8 is a cross-sectional view of an element structure showing an embodiment of a Zener diode corresponding to the embodiment circuit of FIG.

9 is a block diagram of an ignition device system for controlling engine ignition timing using a plurality of the power transistor devices of FIG. 3 or FIG.

[Explanation of Codes] 1, 11, 1 n ... Power transistor device, 2, 21,
2n ... Primary coil, 3 ... Pickup device, 4 ... Battery, 5, 51, 5n ... Secondary coil, 6, 61, 6
n ... spark plug, 7 ... collect electrode, 8 ... base electrode,
9 ... Emitter electrode, 9a, 9b ... N conductivity type region, 10 ...
Zab straight, 11a ... First base region, 11b ... Second base region, 12a ... First pn junction, 12b ... Second p
n-junction, 13 ... Oxide film, 14 ... Protective oxide film, 20 ... Polysilicon film, 21 ... Mask, 22 ... Pn junction, 23, 2
4 ... routing unit, 31 ... channel region 32 ... source region, 33 ... gate electrode, 34 ... source wiring, CON ... contact portion, T ₁ ... power transistor, T ₂ ... driver transistor, Z ... Zener diode, i ... current ,
Vs ... Back electromotive force, Vp ... Secondary voltage, Vz ... Zener voltage, Q ... MOSFET, D1 ... Diode, D2, D3
… Parasitic diodes, R _{1 to} R ₃ … Resistors, SW… Switches, ECN… Engine control unit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 29/90 D

Claims (6)

[Claims] 1. A power transistor, having a collector connected to an inductive load and allowing a switching current to flow according to an input signal, and a plurality of power transistors provided between the collector and the base and configured in series with a polysilicon film. A power transistor device comprising a Zener diode having a pn junction structure. 2. The power transistor device according to claim 1, wherein the polysilicon film on which the Zener diode is formed is formed on the insulating layer on the first main surface of the silicon substrate. 3. The power transistor comprises a pair of Darlington-connected transistors, and a polysilicon film on which the Zener diode is formed is arranged on a base diffusion layer of an input-side transistor on a first main surface of a silicon substrate. The power transistor device according to claim 1 or 2, wherein the power transistor device is provided. 4. The inductive load is a transformer that forms a high voltage supplied to a spark plug, and the power transistor flows in a primary side coil of the transformer in response to an input signal supplied to a base. The power transistor device according to claim 1, wherein the power transistor device forms a current. 5. A MOSFET which is switch-controlled by a control voltage formed on the basis of a Zener current flowing through the Zener diode and which is provided with a MOSFET forming a current path in parallel with the Zener diode. The power transistor device according to claim 1, claim 2, claim 3, or claim 4. 6. The MOSFET has a semiconductor region integrally formed with a collector region of a transistor as a drain, a semiconductor region formed in the drain region as a channel region, and a semiconductor formed in the channel region. A power transistor device, wherein a region is used as a source region, and a gate electrode is provided on a channel region sandwiched between the source region and the drain region via a gate insulating film.