JPH05291241A - Semiconductor device - Google Patents

Abstract

PURPOSE:To relax that a level is formed on the surface of a semiconductor base body, to achieve that an electric field is hardly concentrated and to effectively achieve a high breakdown strength of the semiconductor device by a method wherein a dielectric layer whose interface level with reference to the surface of the semiconductor base body is low is formed so as to come into contact with the surface of the semiconductor base body. CONSTITUTION:In a semiconductor device, a first electrode 3 is formed on the surface side of a semiconductor base body 1 and a second electrode 4 is formed on its rear side. In the semiconductor device, a dielectric layer 5 whose interface level with reference to the surface of the semiconductor base body 1 is formed so as to come into contact with the surface of the semiconductor base body 1. For example, a metal electrode 3 having a field-plate structure is formed on the surface side of a high- resistance semiconductor base body 1 which is composed of an n<+> GaAs layer 11 and an n-GaAs layer 12 in such a way that it is faced with the part of a p-type region 2 formed by a diffusion operation; a rear electrode 4 is formed on the rear side. In addition, a dielectric layer 5 having a low interface level with reference to the surface of the base body 1 composed of AlGaAs or the like is formed so as to come into contact with the surface of the base body 1; a protective film 6 which is composed of SiO2, SiON, SiN or the like is formed on it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a high breakdown voltage.

[0002]

2. Description of the Related Art Heretofore, as a means for increasing the breakdown voltage of a semiconductor device, a method of relaxing an electric field concentration in a semiconductor substrate by taking a field plate structure or a guard ring structure has been taken.

[0003]

The problem to be solved is that the semiconductor substrate is a compound semiconductor, especially gallium arsenide G.
In the semiconductor device in which the first electrode is provided on the front surface side of the semiconductor substrate using aAs and the second electrode is provided on the back surface side thereof, the surface level of the semiconductor substrate is high, and the electric field is easily concentrated on the surface. Depending on the field plate structure and the guard ring structure, it is impossible to achieve a sufficiently high breakdown voltage.

[0004]

According to the present invention, in order to suppress the electric field concentration on the surface of the semiconductor substrate and to sufficiently increase the breakdown voltage, the interface state with the surface of the semiconductor substrate is low in contact with the surface of the semiconductor substrate. A dielectric layer is provided to lower the surface potential of the semiconductor substrate.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a semiconductor device according to the present invention is formed by diffusion on the surface side of a high resistance semiconductor substrate 1 consisting of n (+) layer 11 and n layer 12 of gallium arsenide GaAs. Further, a metal electrode 3 having a field plate structure is provided facing the portion of the p-type region 2, and a back surface electrode 4 is provided on the back surface side of the semiconductor substrate 1, and on the front surface side of the semiconductor substrate 1, A dielectric layer 5 which is in contact with the surface of the semiconductor substrate 1 except the contact portion of the metal electrode 3 and which has a low interface state with the surface of the semiconductor substrate 1 made of, for example, aluminum gallium arsenide.
Is formed, and further SiO ₂ , SiON, Si
A protective film 6 made of N or the like is formed, and the field plate portion of the metal electrode 3 is in contact with the protective film 6.

According to the semiconductor device of the present invention having such a structure, however, the level formation on the surface of the semiconductor substrate 1 is relaxed by the dielectric layer 5, and the electric field concentration is less likely to occur. Is effective for high withstand voltage.

In the figure, 7 indicates a depletion layer.

On the other hand, in the conventional semiconductor device shown in FIG. 3, the surface of the semiconductor substrate 1 is in contact with the surface of the semiconductor substrate 1 except for the contact portion of the metal electrode 3 having the field plate structure to stabilize the surface. Since only the protective film 6 is provided, especially in gallium arsenide GaAs, the electric field concentration caused by the level formed on the surface of the semiconductor substrate 1 becomes remarkable,
It is difficult to achieve a sufficiently high breakdown voltage even if field play means is introduced.

FIG. 2 shows another embodiment of the present invention.
In this case, the metal electrode 8 is opposed to the portion of the p-type region 2 formed by diffusion on the surface side of the semiconductor substrate 1 composed of the n (+) layer 11 and the n layer 12 of gallium arsenide GaAs.
However, a back electrode 4 is provided on the back surface side of the semiconductor substrate 1, and a p-type guard ring 9 is formed on the semiconductor substrate 1, and the metal electrode is provided on the front surface side of the semiconductor substrate 1. 8 except the abutting portion of the semiconductor substrate 1
A dielectric layer 5 having a low interface level with the surface of the semiconductor substrate 1 made of a substance that suppresses the surface level, for example, aluminum gallium arsenide, is formed in contact with the surface of S, and S is further formed thereon.
A protective film 6 made of iO ₂ , SiON, SiN or the like is formed.

Even in the structure as described above, the level formation on the surface of the semiconductor substrate 1 is alleviated by the dielectric layer 5 as in the case of the above-mentioned embodiment, and the electric field concentration hardly occurs. This is effective for increasing the withstand voltage using the guard ring 9.

The present invention is not limited to the one using gallium arsenide GaAs as the semiconductor substrate 1 described above, but it can be effectively carried out in the same manner when another semiconductor substrate is used to effectively increase the breakdown voltage. It goes without saying that you can do it.

[0012]

As described above, according to the semiconductor device of the present invention, the semiconductor substrate 1 is provided by providing the dielectric layer in contact with the surface of the semiconductor substrate and having a low interface state with the surface of the semiconductor substrate.
There is an advantage that the level formation on the surface of the can be relaxed so that electric field concentration is less likely to occur, and the high breakdown voltage can be effectively achieved by a simple means.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a front sectional view showing a semiconductor device according to another embodiment of the present invention.

FIG. 3 is a front cross-sectional view showing a conventional semiconductor device.

[Explanation of symbols]

 1 semiconductor substrate 2 p-type region 3 metal electrode having a field plate structure 4 back electrode 5 dielectric layer 6 protective film 7 depletion layer 8 metal electrode 9 guard ring

Claims (3)

[Claims] 1. A semiconductor device having a first electrode on the front surface side of a semiconductor substrate and a second electrode on the back surface side thereof, in contact with the surface of the semiconductor substrate, and having a low interface state with the surface of the semiconductor substrate. A semiconductor device having a dielectric layer. 2. The protective film is formed on the dielectric layer, the first electrode has a field plate structure, and the field plate portion is in contact with the protective film. The semiconductor device according to the description. 3. The semiconductor device according to claim 1, wherein a protective film is formed on the dielectric layer and a guard ring is formed in the semiconductor substrate.