JP2633048B2 - Field effect transistor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a field-effect transistor device.

2. Description of the Related Art Electric field transistor devices include JFETs, MOSFETs and MESFETs.
Currently, it is widely used as a stone for amplifying and oscillating video and audio of a tuner.

The structure of such a conventionally used field effect transistor will be described with reference to FIG. In FIG. 4, the field-effect transistor device is a compound semiconductor substrate 1
In this, an active layer 2 is formed by ion implantation, then an ohmic metal 3 is formed, and a gate metal 4 is formed. As is apparent from FIG. 4, the portion corresponding to the gate portion of the gate metal 4 was formed with a uniform resistance having a uniform gate length B in the gate width direction A.

Problems to be Solved by the Invention The conventional configuration described above has the following problems.

(1) That is, when the gate portion is used as an oscillation stone, a positive potential is applied to the gate portion, and the gate portion generates heat. As a result, as shown by the temperature curve C in FIG. 5, a large amount of current flows in the gate input section 4a, so that the gate width direction A
Therefore, there is a disadvantage that the heat generation amount in the gate portion is larger in the gate input portion 4a, and the oscillation efficiency is reduced due to a surge breakdown in the gate input portion 4a and a decrease in mobility due to a rise in temperature.

(2) Further, when used for amplifying the image and sound of the channel, the gate section can be expressed by an equivalent circuit D as shown in FIG. 6, the gate input impedance is 50 to 100Ω, and the gate is Internal equivalent circuit resistance is 50 ~ 1
If it is more than 00Ω, there is a problem that the input signal is attenuated in the gate width direction A, and NF (noise figure) and PG (gain) are deteriorated.

The present invention solves the above-described conventional problem, and when used as a power transistor in which a gate potential is applied in a positive direction, it is possible to improve efficiency by making heat generation in a gate portion uniform. In addition, when used as an amplifying transistor in which a high-frequency component enters the gate as an input, a field-effect transistor device that can improve NF and PG by suppressing the attenuation of the input wave at the gate. It is intended to provide.

Means for Solving the Problems In order to solve the above problems, a field effect transistor device of the present invention forms a mask with a gate metal on an active layer generated by ion implantation into a compound semiconductor substrate, and converts the gate metal to a gate electrode. In the field effect transistor device described above, at least the gate electrode is formed such that its thickness is reduced at the tip of the gate.

Operation According to the above configuration, if the resistance decreases in the gate input portion where the current flows in the gate width direction, the temperature rise in the gate input portion decreases, the heat generation in the gate portion becomes uniform, and the efficiency with the oscillation stone decreases. To improve the performance of the device.

Conversely, if the resistance is reduced in the gate width direction from the gate input to the gate tip, signal attenuation at the gate is prevented. Thereby, the performance of the NF and PG of the element is improved, and the performance of the used equipment is improved.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a top view of a field effect transistor device showing one embodiment of the present invention.

In FIG. 1, the field-effect transistor device has a structure in which an active layer 12 is formed in a compound semiconductor substrate 11 by ion implantation, an ohmic metal 13 is formed, and a gate metal 14 is formed. Here, the mask for forming the gate metal 14 is formed from the gate input portion 14a to the gate tip portion 14b.
It is formed thinner toward. As a result, the gate portion of the field-effect transistor has a larger gate length as the gate input portion 14a to reduce the resistance, and the gate portion is formed in a triangular shape in which the resistance per unit length increases toward the gate tip portion 14b. I have. That is, the gate portion of the field effect transistor is not formed with a uniform resistance in the gate width direction. As described above, by reducing the resistance value of the gate portion in the gate width direction toward the gate input portion 14a, heat generation of the gate input portion 14a when a positive potential is applied to the gate portion can be reduced.

FIG. 2 shows a heat generation state of the gate portion when a large positive input signal is applied to the field effect transistor. As can be seen from the temperature curve E in FIG. 2, since the resistance value is smaller at the gate input portion 14a, the heat generation at the gate input portion 14a of the gate portion is suppressed lower than that of the conventional device shown in FIG. It can be seen that heat generation in the gate portion is uniform.

FIG. 3 shows a comparison of the oscillation efficiency between the field-effect transistor of the present invention and the conventional field-effect transistor. As can be seen from FIG. 3, by making the temperature of the gate portion uniform, the oscillation efficiency F of the field effect transistor of the present invention can be reduced by the oscillation efficiency G of the conventional field effect transistor.
This shows that the present invention is more effective in improving the characteristics of efficiency than that of.

In the present embodiment, the gate input portion is formed such that the gate length is formed thicker and the gate length is formed thinner toward the tip of the gate, but emphasis is placed on the attenuation of a small signal input to the gate portion. As a use, contrary to the above, the gate length may be increased from the gate input to the gate tip. In addition, the above object can be similarly achieved by making the thickness of the gate metal non-uniform.

Effect of the Invention As described above, according to the field effect transistor device of the present invention, when the device is used as an oscillation stone, if the resistance is smaller at the gate input portion, the heat generation at the gate portion can be made uniform, and transmission can be performed. It is possible to improve efficiency and efficiency for oscillation. Conversely, if the resistance is smaller at the tip of the gate, the attenuation of the input wave can be suppressed at the gate, and the NF, PG can be used for tuner reception.
Can be improved, and higher performance of the set can be obtained.

[Brief description of the drawings]

FIG. 1 is a top view of a field-effect transistor device showing one embodiment of the present invention, FIG. 2 is a temperature distribution diagram at various locations in the width direction of a gate portion of the field-effect transistor device, and FIG. FIG. 4 is a top view of a conventional field-effect transistor device, and FIG. 5 is a temperature distribution diagram at each position in a width direction of a gate portion of the field-effect transistor device. FIG. 6 is a diagram showing an equivalent circuit of the gate unit. 14: Gate metal, 14a: Gate input section, 14b: Gate tip.

Claims (1)

(57) [Claims] 1. A field effect transistor device having a gate metal formed as a mask on an active layer formed by ion implantation into a compound semiconductor substrate and using the gate metal as a gate electrode. A field-effect transistor device formed to be thin at the tip of the gate.