JPH025569A - Static induction transistor - Google Patents

Abstract

PURPOSE:To obtain a static induction transistor, in which it grows to be non-conductive between a source and a drain through VGS of a small value, by a method wherein a part of a channel region, constituted between a source region and a drain region, is made to be of a second conductivity type. CONSTITUTION:This static induction transistor is possessed of an N-type source region 1, an N-type drain region 2, and a P-type gate region 3 and a channel region 4 is composed of a P-type first channel region 5 and an N-type second channel region 6. In a case that VDS is made to increase with VGS fixed at zero volt, it grows into a conductive state between the drain region 2 and the source region 1 when the P-type first channel region becomes depleted with the increase of a reverse bias voltage between the N-type drain region 2 and the P-gate region 3 and a potential barrier between the N-type source region 1 and the P-type first channel region 5 becomes small enough. In a state that the value of VDS is small before the transistor is put under the above potential condition, a drain current does not flow between the N-type source region 1 and the drain region 2, and the transistor can be possessed of a characteristic equivalent to that of a conventional static induction transistor under such a condition that the value of VDS is large after it is put under the above potential condition.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to static induction transistors.

[Conventional technology]

Conventionally, the channel region of a static induction transistor has been comprised of a semiconductor layer of the same conductivity type as the source region and drain region.

FIG. 3 is a schematic cross-sectional view of an example of a conventional static induction transistor.

This static induction transistor is composed of an N-type source region 1, an N-type drain region 2, a P-type gate region 3, and an N-type channel region 7.

In a conventional static induction transistor having such a structure, current/voltage characteristics as shown in FIG. 4 are obtained. Fourth
The horizontal axis in the figure is the drain-source voltage Vos (volts),
The vertical axis is the drain current In (ampere), with the gate-source voltage VGS (volt) as a parameter. It has diode characteristics where the rising voltage changes depending on the VOS. As for the values of V and g, a negative voltage of 0 volt or less is usually applied so that the PN junction between the gate and source does not become forward biased.

[Problem to be solved by the invention]

If the VGS value is close to O volts, at least VGS is 0
In the case of volts, the channel region is the same N-type region as the source and drain regions, so even if D5 is O volts, the source and drain are in a conductive state. Therefore, as soon as VDS has a slightly positive value from O volts, ID begins to flow. That is, when VGS in FIG. 4 is 0 volts, the slope of the current/voltage characteristics near the origin is not 0. However, in many applications, it is desired that the capacitor be completely non-conductive when VDS is a sufficiently small value close to O volts, and become conductive only when VDS is a certain high value. In order to obtain such characteristics, conventional electrostatic induction transistors have the disadvantage that a relatively large negative value must be applied as the VGS value.

An object of the present invention is to provide a static induction transistor in which the source and drain become non-conductive at a small VGg value.

[Means to solve the problem]

The present invention provides a static induction transistor having a source region and a drain region of a first conductivity type and a gate region of a second conductivity type opposite to the first conductivity type, in which a region between the source region and the drain region is provided. A part of the channel region formed in is of the second conductivity type.

[Effect]

According to the structure of the present invention, since the region of the opposite conductivity type in the channel region forms a potential barrier due to a built-in potential with respect to carriers flowing from the source region to the drain region, V
Even when Gs is 0 volts, it is possible to realize the characteristic that the source and drain are in a non-conductive state when VDs is small.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention.

The static induction transistor of this embodiment has an N-type source region 1, an N-type drain region 2, and a P-type gate region 3, and a channel region 4 includes a P-type first channel region 5, an N-type second channel region
It is composed of a channel region 6. This example is a so-called N-type static induction transistor in which the carriers contributing to the drain current are electrons, but if the conductivity types of each region are all reversed, the carriers contributing to the drain current are holes. A certain P-type static induction transistor can be constructed.

In this embodiment, in a thermal equilibrium state where VGS is O volts and VDS is O volts, a built-in potential is generated between the N-type source region 1 and the P-type first channel region 5, and this is generated in the N-type source region 1. Since it acts as a potential barrier for electrons, a characteristic is obtained in which the N-type source region 1 and the N-type drain region 2 are in a non-conductive state. Fix the VGS to the O bolt, and
When Ds is increased, conduction occurs because the P-type first channel region 5 is depleted as the reverse bias voltage between the N-type drain region 2 and the P-type gate region 3 increases, and the N-type This is when the potential barrier between the source region 1 and the P-type first channel region 5 becomes sufficiently small. In the state where the value of VDS is small until such a potential condition is reached, no drain current flows between the N-type source region 1 and the N-type drain region 2. When the value is large, it is possible to obtain characteristics equivalent to those of conventional static induction transistors.

FIG. 2 shows the current/voltage characteristics obtained in this example.

The current-voltage characteristics of the conventional static induction transistor shown in Figure 4 are shifted in parallel along the horizontal axis, and in the small VOS region ■, even when 5 is 0 volts, the drain It has the characteristic that no current flows.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a static induction transistor having a characteristic that no drain current flows in a small VDS region regardless of the value of VGS. In addition, the value of VDS at which the drain current begins to flow can be controlled by changing the impurity concentration or thickness of the channel region of the opposite conductivity type to the source region and drain region, increasing the degree of freedom in circuit design. There are also advantages.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention, and FIG.
A characteristic diagram showing the current-voltage characteristics of the embodiment shown in the figure, FIG. 3 is a schematic cross-sectional diagram of an example of a conventional electrostatic induction I transistor,
FIG. 4 is a characteristic diagram showing the current-voltage characteristics of the conventional example shown in FIG. 1... N-type source region, 2... N-type drain region,
3...P-type gate region, 4...channel region 5.
. . . P-type first channel region, 6 . . N-type second channel region, 7 . . . N-type channel region. My agent friend, patent attorney Shinji Uchihara? Flash

Claims (1)

[Claims] The source region and drain region of the first conductivity type and the first
In a static induction transistor having a gate region of a second conductivity type opposite to the conductivity type, a part of the channel region formed between the source region and the drain region is of the second conductivity type. Characteristics of static induction transistors.