JPH0364065A - Semiconductor device - Google Patents

Abstract

PURPOSE:To lower frequency characteristic of a simple transistor structure, to eliminate influence of external noise and radio wave and to prevent the erroneous operation of a transistor by incorporating a capacitor in the same substrate formed of a transistor active region. CONSTITUTION:A bipolar npn transistor is composed of a n-type epitaxial Si substrate 1 to become a collector, a n<+>-type collector leading part 2, a base p-type diffused layer 3 and an emitter n<+>-type diffused layer 4. A junction capacitance forming p-type diffused layer 5 is provided in the substrate 1 to form a p-n junction capacitance C1 between it and the collector n<->-type layer. When the capacitance (C1) by the p-n junction is inserted between the base and the emitter of the transistor, high frequency characteristics can be lowered, and its structure can be simplified as compared with a conventional structure in which a by-path is externally provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device mainly consisting of a transistor, and particularly to a semiconductor device for automobile parts having a structure that is hardly affected by external noise, induced radio waves, etc.

[Prior Art] Recently, the electronicization of automobile parts has progressed rapidly, and the number of display devices such as lamps and LEDs attached to dashboards and the like is increasing. These display devices require display transistors to drive them, but at the same time, these transistors are protected against the influence of external noise such as radio wave oscillations from car phones and personal radios installed in the car, and radio waves emitted from the engine. It is known to be easy to receive.

That is, when the DC level of the input (0MOS output) of the driving transistor (display transistor) is OFF, the output of the transistor is naturally OFF, and the display device connected to the output system is turned off, for example. When radio waves or noise enter the input system of the driving transistor in this state, the signal component is amplified and an output appears. As a result, the display device malfunctions.

On the other hand, in general, the drive transistor shown in FIG.
As shown in FIG. 13, this is handled by providing an external bypass using a capacitor or the like. However, this has the disadvantage that the number of parts increases, the board mounting area increases, and the cost increases.

[Problem to be solved by the invention] If the display (drive) transistor has a low frequency characteristic (fT) that is not affected by noise, radio waves, etc., an external capacitor etc. is not necessarily necessary. It can be said that there is no.

In general, effective means for lowering the ft of a transistor include increasing the base width, increasing the collector capacitance, and increasing the collector resistance.

However, increasing the collector resistance deteriorates the DC characteristics (hFE linearity, γCε5at), etc., and increasing the base width and collector capacitance inevitably increases the size of the transistor, which is not preferable.

The present invention has been made in consideration of the above points, and its purpose is to provide a semiconductor device for automobile parts that does not require the use of external capacitors or change the size, and also reduces the f-characteristics of transistors. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a semiconductor device in which an active region of a transistor and two electrodes connected thereto are formed on one main surface of a semiconductor substrate, A capacitor, for example a junction capacitor, is provided in a portion of the main surface outside the active region and is connected in a direction that reduces the frequency characteristics of the transistor.

[The f〒 characteristic of a transistor for action driving is generally determined by the following formula (%) (τ hill, τB... is the time constant of the emitter, base...) To lower fT, the base diffusion layer, the emitter There is a way to make the diffusion layer deeper and further widen the base width. That is, optimization of τB. It is also possible to increase τX and τC, but the DC characteristics (hFE linearity, γc
I:csat), etc., resulting in secondary problems with respect to the blunting of only the high frequency characteristics, which is the purpose of the present invention.

In the present invention, the resistance component and capacitance component included in τ and τC, (ta=γe(Ci +Cc), tc=γsc'
Cc) That is, fT is reduced by arranging a capacitor that increases Cc and Cc.

[Example] Hereinafter, the present invention will be described with reference to the drawings regarding several examples.

FIG. 1 is a longitudinal cross-sectional view showing an example of a case where a junction capacitance is built into a semiconductor substrate in which a transistor functional region is formed.

1 is an n epitaxial Si substrate serving as a collector, 2 is an n+ collector extraction portion (substrate), 3 is a base P diffusion layer, and 4 is an emitter n+ diffusion layer, which constitute a bipolar npn transistor. 5 is a P diffusion layer for junction capacitance type, which creates a Pn junction capacitance C□ between it and the collector n-layer.

6 is an oxide film (Sin, film), through the hole of this oxide film A
The Q electrode film 7 makes ohmic contact with the diffusion region and connects the base and the junction capacitance C1.

In FIG. 3, the base 2 layer 3 in the semiconductor device of FIG. 1 is extended as is and used as a junction capacitance with the collector.

In these semiconductor devices, a Pn junction (
By inserting a capacitor (C□) formed by a junction diode), the high frequency characteristics can be lowered, and the structure is simpler and less bulky than the conventional structure in which an external bypass is provided.

Figure 4 shows an example in which P diffusion layers 8 and 9 for forming junction capacitance are provided on both sides of the active region of the transistor, one being connected to the base and the other being connected to the emitter. As a result, as shown in the equivalent circuit diagram in FIG. 5, a Pn junction capacitance (ci=cz) is interposed between the collector and base and between the collector and emitter to obtain the same effect.

FIG. 6 shows an example of this application, and is an equivalent circuit diagram of a semiconductor device when the semiconductor device is connected so that a Pn junction capacitance (C1°CS) exists between the base and collector and between the base and emitter.

FIG. 7 shows an example in which the junction diode in FIG. 1 is replaced with a transistor and its base-collector junction capacitance is utilized.As shown in the equivalent circuit diagram of FIG. 8, two transistors (vyu) are used.

γ8) are connected in parallel.

In this case, a transistor replaces a junction diode (〒12)
A transistor whose hFE is sufficiently smaller than that of the drive transistor (〒γ,) is used. The characteristics of the transistor structure will vary somewhat as a result, but if optimization is performed, such as setting hFE of transistor structure 2 so that the width factor (hFE) of the entire semiconductor device is greater than the required value, the implementation described above can be achieved. The same effect as in the example (FIGS. 1 to 4) can be obtained.

FIG. 9 is a longitudinal sectional view showing an example in which a MOS capacitor is built in the same main surface of a substrate in which a transistor active region is formed.

10 is a thin insulating film (SiO, film) made of semiconductor (SiO)
) on the substrate, and form the Afi electrode @l as a metal electrode on this to constitute the MOS capacitor C4.
The Q electrode is connected to the base electrode of the transistor.

If the film thickness of this Sin is made thinner, the MOS capacitance C4
It's - it's getting bigger.

FIG. 10 is an equivalent circuit diagram of this semiconductor device.

In this semiconductor device, an extraction electrode portion 1 of a MOS capacitor
1 may be connected from the emitter electrode.

Alternatively, similar effects can be obtained when both the base and emitter electrodes are connected simultaneously as shown in the equivalent circuit diagram of FIG.

[Effects of the Invention] According to the present invention described in the embodiments above, the following effects can be achieved.

By incorporating a capacitor in the same substrate on which the transistor active region is formed, a simple transistor structure is possible.
It reduces the characteristics and eliminates the influence of external noise and radio waves, preventing transistor malfunctions and improving the reliability of automotive parts.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a semiconductor device showing an embodiment of the present invention. FIG. 2 is an equivalent circuit diagram corresponding to FIG. 1. FIG. 3 is a longitudinal sectional view showing a modification of the semiconductor device shown in FIG. 1. FIG. 4 is a longitudinal sectional view of a semiconductor device showing another embodiment of the present invention. FIG. 5 is an equivalent circuit diagram corresponding to FIG. 4. FIG. 6 is an equivalent circuit diagram corresponding to a modified example of the device shown in FIG. 4. FIG. 7 is a longitudinal sectional view of a semiconductor device showing another embodiment of the present invention. FIG. 8 is an equivalent circuit diagram corresponding to FIG. 7. No. 9rJA is a longitudinal sectional view of a semiconductor device showing another embodiment of the present invention. FIG. 10 is an equivalent circuit diagram corresponding to FIG. 9. FIG. 11 is an equivalent circuit diagram corresponding to a modified example of the device shown in FIG. 9. FIG. 12 is a longitudinal sectional view of a conventional semiconductor device. FIG. 13 is an equivalent circuit diagram corresponding to the device of FIG. 12. 1... Collector (n-semiconductor layer) 3... Base (P) diffusion layer 4... Emitter (n+) diffusion layer 5... Diffusion layer for forming junction capacitance 7... All electrode film 10... S i O , Film 1 Figure 1

Claims (1)

[Claims] 1. A semiconductor device in which an active region of a transistor and two electrodes connected thereto are formed on one main surface of a semiconductor substrate, and a capacitor is provided in a portion of the main surface outside the active region. ,
A semiconductor device characterized in that the transistors are connected in a direction that reduces frequency characteristics. 2. In the semiconductor device according to claim 1, the capacitance is a junction capacitance. 3. In the semiconductor device according to claim 1, the capacitor is a MOS capacitor.