JP2003109972A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which prevents a drop in breakdown strength between a gate electrode and a drain electrode. SOLUTION: The semiconductor device is provided with a semiconductor substrate 11 on which an active layer 12 is formed, an ohmic contact source electrode S formed on the active layer 12, a ohmic contact drain electrode D formed on the active layer, and a Schottky junction gate electrode G installed inside a recess 13 formed by digging the active layer. A groove 14 in a prescribed depth is formed on the active layer between the recess 13 and the drain electrode D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high breakdown voltage of a semiconductor device suitable for ultrahigh frequency operation, for example, a field effect transistor.

[0002]

2. Description of the Related Art A conventional semiconductor device will be described with reference to FIG. 4 by taking a field effect transistor used as an amplifying element for an ultra high frequency signal as an example.

An active layer 42 is formed on a semiconductor substrate 41, and an ohmic contact source electrode S and a drain electrode D are formed on the active layer 32. In addition, the source electrode S
A recess 33, which is formed by cutting a part of the active layer 32, is provided on the active layer 32 located between the drain electrode D and the drain electrode D, and a Schottky junction gate electrode G is formed in the recess 33.

[0004]

Conventional semiconductor devices, such as field effect transistors, are required to have higher performance and lower source resistance. Examples of methods for reducing the source resistance include a method of reducing the distance between the source electrode and the gate electrode, a method of increasing the thickness of the active layer, and a method of doping the active layer with a high concentration.

However, the structure of thickening the active layer or the structure of increasing the concentration of the active layer has a problem that the breakdown voltage between the gate electrode and the drain electrode is lowered.

It is an object of the present invention to solve the above-mentioned drawbacks and to provide a semiconductor device in which the breakdown voltage between the gate electrode and the drain electrode is prevented from lowering.

[0007]

According to the present invention, there is provided a semiconductor substrate having an active layer formed thereon, an ohmic contact source electrode provided on the active layer, and an ohmic contact provided on the active layer. A drain electrode and a gate electrode of a Schottky junction provided in a recess in which the active layer is dug, a trench having a predetermined depth on the active layer between the recess and the drain electrode. Is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows an embodiment of the present invention.
Will be described with reference to. Reference numeral 11 is a semiconductor substrate such as GaAs, and an active layer 12 is provided on the semiconductor substrate 11. Further, a source electrode S and a drain electrode D, which are in ohmic contact, are provided on the active layer 12 at predetermined intervals. On the active layer 12 located between the source electrode S and the drain electrode D, a recess 13 formed by digging a part of the active layer 12 to a predetermined depth is provided, and a Schottky junction gate electrode G is formed in the recess 13. It is provided. Further, a groove 14 having a predetermined depth is formed in a part of the active layer 12 between the recess 13 provided with the gate electrode G and the drain electrode D.

In the above structure, the thickness of the active layer 12 located outside the recess 13 is t, the thickness of the active layer 12 located below the groove 14 is t1, and the thickness of the active layer 12 is located below the gate electrode G. When the thickness of the active layer 12 is t2,
The respective thicknesses t, t1, t2 are set to satisfy the relation of t>t1> t2.

In this case, the thickness t1 of the active layer 12 located below the groove 14 is made larger than the thickness t2 of the active layer 12 located below the gate electrode G.
The drain current is not limited at the portion 4 and even if the groove 14 is provided, it does not hinder an increase in power.

According to the above structure, the electric field is relaxed in the groove 14. As a result, it is possible to realize a semiconductor device such as a field effect transistor in which the breakdown voltage between the gate electrode G and the drain electrode D is improved without increasing the source resistance.

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 2, portions corresponding to those in FIG.

In this embodiment, the first recess 21 is formed by engraving a wide area of the active layer 12 located between the source electrode S and the drain electrode D. In addition, the active layer 12 in the first recess 21 is partially dug into a second
The recess 22 is formed, and the Schottky junction gate electrode G is provided in the second recess 22. Then, in the first recess 21, the second recess 22 provided with the gate electrode G is formed.
A groove 23 having a predetermined depth is formed between the drain electrode D and the drain electrode D.

In the above structure, the thickness of the active layer 12 located outside the first recess 21 is t, and the thickness of the active layer 12 in the portion of the second recess 22 where the groove 23 is not provided. t0, the thickness of the active layer 12 located below the groove 23 is t1, and the active layer 12 located below the gate electrode G.
When the thickness of each is t2, the respective thicknesses t, t0,
t1 and t2 are set to satisfy the relationship of t>t0>t1> t2.

Also in this case, since the thickness t1 of the active layer 12 located below the groove 23 is made larger than the thickness t2 of the active layer 12 located below the gate electrode G, the groove 23 of the groove 23 is formed. The drain current is not limited at the portion, and the provision of the groove 14 does not hinder the increase in power consumption.

According to the above structure, the electric field is relaxed in the groove 23, and the breakdown voltage between the gate electrode G and the drain electrode D can be improved without increasing the source resistance.

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 3, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and overlapping description will be partially omitted.

In this embodiment, the end portion 21a of the drain electrode D of the first recess 21 and the end portion 23a of the drain electrode D of the groove 23 coincide with the groove 23 formed on the active layer 12 in the first recess 21. It is provided at the position where Also in this case, the electric field is relaxed in the groove 23, and the breakdown voltage between the gate electrode G and the drain electrode D is improved without increasing the source resistance.

In each of the above embodiments, the case where the active layer has a single layer structure has been described. However, the present invention is not limited to the case where the active layer has a single layer structure, but can be applied to a multilayer structure such as HEMT or HFET.

[0020]

According to the present invention, it is possible to realize a semiconductor device in which the breakdown voltage between the gate electrode and the drain electrode is prevented from decreasing.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining an embodiment of the present invention.

FIG. 2 is a sectional view for explaining another embodiment of the present invention.

FIG. 3 is a sectional view for explaining another embodiment of the present invention.

FIG. 4 is a cross-sectional view for explaining a conventional example.

[Explanation of symbols]

11 ... Semiconductor substrate 12 ... Active layer 13 ... Recess 14 ... Groove S ... Source electrode D ... Drain electrode G ... Gate electrode t ... Active layer thickness t1 outside region of the recess ... Thickness t2 of the active layer located at the bottom of the active layer located below the gate electrode

Claims (4)

[Claims] 1. A semiconductor substrate having an active layer formed thereon, an ohmic contact source electrode provided on the active layer, an ohmic contact drain electrode provided on the active layer, and the active layer. In a semiconductor device having a Schottky junction gate electrode provided in a recessed portion, a groove having a predetermined depth is provided on an active layer between the recess and the drain electrode. Semiconductor device. 2. The thickness of the active layer located below the trench is t
1. The thickness of the active layer located below the gate electrode is t
2. The semiconductor device according to claim 1, wherein there is a relationship of t>t1> t2, where t is a thickness of the active layer in a region where no groove is formed outside the recess. 3. A semiconductor substrate having an active layer formed thereon, an ohmic contact source electrode provided on the active layer, an ohmic contact drain electrode provided on the active layer, and the source electrode. And a semiconductor device having a first recess in which the active layer is dug between the drain electrodes, and a Schottky junction gate electrode provided in a second recess in which the active layer is dug in the first recess. The semiconductor device according to claim 1, wherein a groove having a predetermined depth is provided on the active layer in the first recess located between the gate electrode and the drain electrode. 4. The thickness of the active layer located below the trench is t1, the thickness of the active layer located below the gate electrode is t2, and the thickness of the active layer located outside the first recess. Where t is t, and t is the thickness of the active layer in the region where the groove is not formed in the first recess, t> t0
The semiconductor device according to claim 3, wherein there is a relationship of>t1> t2.