JPH0684955A - Field effect transistor - Google Patents

Abstract

PURPOSE:To obtain a field effect transistor having a short gate length, a small resistance and a T-shaped gate electrode which is scarcely tilted down. CONSTITUTION:An air bridge 1 made of a conductor or an insulator is provided between adjacent gate electrodes 20 to reinforce the electrode 20. Thus, a T-shaped gate is reinforced to reduce a fraction defectiveness such as tilt-down of the gate and to improve yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect transistor having a T-shaped gate electrode used as a low noise amplifier or a high output amplifier.

[0002]

2. Description of the Related Art In a field effect transistor having a gate, a source and a drain, it is necessary to shorten the gate length for the purpose of reducing noise. However, when the gate length is shortened, the gate resistance increases. Therefore, as shown in FIG. 5, the gate has a T shape to reduce the resistance T.
Type gate field effect transistors are used. In the figure, 10 is a substrate, on the surface of which a gate electrode 20 having a T-shaped cross section (hereinafter, T-shaped gate electrode) 20 is arranged,
The drain electrodes 3 are formed on both sides of the T-shaped gate electrode 20.
0, the source electrode 40 is formed.

Next, the operation will be described. For example, as the field effect transistor, a GaAs Schottky gate F
When considering ET (hereinafter MESFET), semi-insulating G
A substrate 10 having thin N-type GaAs on an aAs substrate is used, and when a negative voltage is applied to the gate electrode 20, electrons are pushed below the gate electrode 20 and a depletion layer is formed below the gate electrode 20. The current flowing between the drain electrode 30 and the source electrode 40 is suppressed by the spread of the voltage, so that the current flowing between the drain and source electrodes 30 and 40 can be controlled by the magnitude of the voltage applied to the gate electrode 20. .

As described above, it is generally known that the field effect transistor reduces noise and the like by shortening its gate length. However, if the gate length is simply shortened, the resistance will increase and the gain and the like will decrease. Therefore, the gate resistance can be reduced by adding a large conductor to the upper portion of the normal gate electrode so as not to contact other electrodes like the T-type gate in FIG.

[0005]

Since the conventional field effect transistor is constructed as described above, it has a large conductor layer above the gate. There is a problem that the weight of the upper part of the gate causes the gate to fall and the manufacturing yield is reduced.

The present invention has been made to solve the above problems, and an object thereof is to obtain a field effect transistor in which the gate resistance is reduced and the gate electrode does not collapse during manufacturing.

[0007]

In the field effect transistor according to the present invention, the upper part of the T-type gate electrode and the source / drain electrodes arranged on the surface of the substrate are connected by a bridging member made of an insulator.

Further, adjacent gates are connected by an air bridge. Further, an insulator is used below the air bridge to provide leg portions for connecting the air bridge and the source / drain electrodes arranged on the substrate surface.

[0009]

According to the present invention, the T-shaped gate electrode is reinforced by supporting the T-shaped gate from both sides with the bridging member or by connecting the adjacent T-shaped gates by the air bridge, and the T-shaped gate electrode is prevented from falling down. The resistance can be reduced.

[0010]

【Example】

Example 1. FIG. 1 is a perspective view of a field effect transistor according to a first embodiment of the present invention.
5 shows a state in which a type gate is formed. In the figure, the same reference numerals as those in FIG. 5 denote the same or corresponding portions, and 1 is an air bridge composed of an electric conductor or an insulator, and is provided between adjacent T-type gates 20. Hold at appropriate intervals.

Such an air bridge can be formed by, for example, a method of simultaneously forming the gate electrode 10 by photolithography, etching or the like, or by a process different from the step of forming the gate electrode 10.

As described above, according to this embodiment, the air bridge 1 made of a conductor or an insulator is provided between the T-shaped gates 20.
Since the gate electrodes 20 are provided appropriately,
The rigidity of the gate electrode is improved, and the gate electrode is reinforced so that it does not easily fall. Further, by forming the air bridge 1 with a conductor, reduction of gate resistance can be expected.

When forming the air bridge 1 using a conductor in this embodiment, a conductor other than the material forming the gate electrode 11 may be used.

Example 2. Next, a field effect transistor according to a second embodiment of the present invention will be described with reference to FIG. In this embodiment, in order to reinforce the air bridge itself formed between the gate electrodes, leg portions connected to the source or drain electrode are provided below the air bridge. In the figure, 2 is an air bridge according to the present embodiment,
A bridge portion 2a connecting the gate electrodes 20 and the bridge portion 2a
a leg portion 2b which is provided below a and has one end connected to the bridge portion 2a and the other end connected to the source or drain electrode (in the figure, the portion connected to the drain electrode 30) made of an insulator It is configured.

Thus, the air bridge itself has a cross section T.
With the V-shaped structure, the space between the gate electrodes 20 can be reinforced, and the rigidity of the air bridge itself can be increased, resulting in high reliability. In this embodiment, the bridging portion 2a forming the air bridge 2 is the leg portion 2
It may be the same member as the member forming b or may be a different member.

Embodiment 3. Next, a field effect transistor according to a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a plurality of T-shaped gates formed on the same substrate are connected by using a single air bridge formed over the entire surface of the gate electrode. In FIG. 3, reference numeral 3 is an air bridge formed so as to connect the adjacent gate electrodes 20 over the entire surface, and is formed using a conductor or an insulator. Such an air bridge can be obtained by integrally forming with the gate electrode or by using a conductor or an insulator in another step.

By doing so, the number of connecting portions between the respective gate electrodes is increased, the rigidity of the gate electrode 20 can be further increased, and the use of a conductor for the air bridge further reduces the gate resistance. You can also plan.

In this embodiment, the structure of the second embodiment may be applied so that the structure of the air bridge itself is T-shaped in cross section so as to increase the rigidity of the air bridge itself.

Example 4. Next, a field effect transistor according to a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, in a field effect transistor having one T-type gate on a substrate, an air bridge connecting the upper part of the gate electrode and the source and drain electrodes is formed on both sides of the gate electrode in order to improve the rigidity of the gate electrode. It was done like this. In the figure, 4 is an air bridge formed so as to be connected to the upper portion of the T-shaped gate electrode 20, the drain electrode 30 and the source electrode 40 arranged on the surface of the substrate 10 on both sides of the gate electrode 20, respectively.

By doing so, the reliability of the field effect transistor having a single T-type gate electrode can be improved.

In each of the above embodiments, the MESFET has been described as an example, but the present invention may be applied to a MOSFET.

[0022]

As described above, according to the field effect transistor of the present invention, the T-type gate electrodes are supported by providing the bridge portions made of the insulator on both sides thereof, or the adjacent T-type gates are electrically connected to each other. Alternatively, since they are connected by an insulator, the gate electrode is less likely to collapse in the step after the T-type gate electrode is formed, and the yield of defective products is reduced and the yield is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a field effect transistor having a T-type gate according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a field effect transistor having a T-type gate according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a field effect transistor having a T-type gate according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a field effect transistor having a T-type gate according to a fourth embodiment of the present invention.

FIG. 5 is a view showing a field effect transistor having a conventional T-type gate.

[Explanation of symbols]

 1 Air Bridge 2 Air Bridge 2a Bridge Part 2b Leg 3 Air Bridge 4 Air Bridge 10 Substrate 20 T-type Gate Electrode 30 Drain Electrode 40 Source Electrode

Claims (4)

[Claims] 1. A field effect transistor comprising a gate electrode having a T-shaped cross section formed on a substrate, and source / drain electrodes arranged on the surface of the substrate on both sides of the gate electrode. A field effect transistor, characterized in that the source and drain electrodes are connected by a bridging member made of an insulator. 2. A field effect transistor comprising: a plurality of gate electrodes having a T-shaped cross section formed on a substrate; and source / drain electrodes arranged on the surface of the substrate on both sides of each of the gate electrodes. A field effect transistor, characterized in that a bridge portion made of an insulating material or a conductive material for coupling the gate electrodes is provided. 3. The field effect transistor according to claim 2, further comprising a leg portion formed of an insulator and connecting the bridge portion and the source / drain electrode. 4. The field effect transistor according to claim 2, wherein the bridge portion is formed over the entire surface between adjacent gate electrodes.