JPH04162678A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent damage of a boundary, generation of a leakage current between a gate and a source or a drain by providing a step of simultaneously forming a field oxide film and a gate oxide film, and a step of removing the oxide film of a gate part except a predetermined thickness in a high voltage P-channel transistor of a high charge MOS IC. CONSTITUTION:A high voltage P-channel transistor in which a field oxide film 5 and a gate oxide film 6 are simultaneously formed, is formed of a source voltage 1, polysilicon 2 of a gate, a drain electrode 3, a PSG 4 of an interlayer film, a field oxide film 5, a gate oxide film 6, and a junction 7 of the field oxide film and the gate oxide film. The field oxide film of about 1.8mum of thickness is formed on the entire surface, the oxide film of the gate part is etched to form the film 6. Accordingly, deterioration of an oxide film properties of a boundary between the films 5 and 6 is eliminated. Thus, damage of the gate oxide film, generation of a leakage current between the gate and a source or a drain can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a gate oxide film of a high voltage P-channel transistor of a high breakdown voltage MO5IC.

FIG. 3 shows the structure of an output P-channel transistor of a high-voltage MO5IG, which is used as a driver for a conventional high-voltage display.

In FIG. 3, 1 is a source electrode, 2 is a gate polysilicon, 3 is a drain electrode, 4 is an interlayer film PSG, 5 is a field oxide film, 6 is a gate oxide film, and 7 is a field oxide film and a gate oxide film. It is the joint of

When a high negative voltage is applied to the gate polysilicon 2, a P-type inversion layer is formed under the gate oxide film 6, allowing current to flow between the source electrode 1 and the drain electrode 3.

(2) By the way, in the above transistor, the field oxide film 5 is formed in FIG. 4(B), and then the gate oxide film 6 is formed in FIG. 4(C).

Therefore, the quality of the oxide film deteriorates at the boundary part 7 between the field oxide film 5 and the gate oxide film 6 due to insufficient supply of oxygen, heavy metals, dust, etc., and when a high voltage is applied to the gate, the boundary part may be destroyed or the gate oxide film 6 may be damaged. This has the drawback of generating leakage current between the source and drain.

In order to solve the above-mentioned problem, this invention is characterized by including a step of simultaneously forming a field oxide film and a gate oxide film, and a step of removing the oxide film in the gate portion leaving only a predetermined thickness. That is.

1. The above manufacturing method eliminates deterioration of the oxide film quality at the boundary between the field oxide film and the gate oxide film, improving the withstand voltage between the gate, source, and drain, preventing destruction of the gate oxide film, and preventing damage to the gate, source, and drain. It is also possible to prevent leakage current from occurring between the drains.

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows a cross-sectional view of a high voltage P-channel transistor in which a field oxide film and a gate oxide film are simultaneously formed according to an embodiment of the present invention. The names and operating principles of each part are the same as those shown in FIG. 3 above, so explanations will be omitted.

FIGS. 2(A) to 2(E) show cross-sectional views according to the manufacturing flow of this transistor.

By forming a field oxide film with a thickness of about 1.8 um on the entire surface as shown in FIG. 2(B), and etching the oxide film on the gate part in FIG.
A human gate oxide film 6 is formed.

, This method consists of a field oxide film 5 and a gate oxide film 6.
This eliminates deterioration of the oxide film quality at the boundary, which has the advantage of preventing damage to the gate oxide film at the boundary and leakage current between the gate, source, and drain.

As described above, this invention eliminates the boundary between the field oxide film and the gate oxide film by forming the field oxide film and the gate oxide film at the same time. This has the effect of preventing leakage current between the drains.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a high voltage P-channel transistor in which a field oxide film and a gate oxide film are simultaneously formed according to the present invention. FIGS. 2A to 2E are cross-sectional views showing a manufacturing flow of a high-voltage P-channel transistor in which a field oxide film and a gate oxide film are simultaneously formed according to the present invention. FIG. 3 is a cross-sectional view of a conventional high voltage P-channel transistor in which a field oxide film and a gate oxide film are formed separately. FIGS. 4A to 4E are cross-sectional views showing the manufacturing flow of a conventional high-voltage P-channel transistor in which a field oxide film and a gate oxide film are formed in separate steps. 1... Source electrode, 2... Gate polysilicon, 3...
Drain electrode, 4... PSGl of interlayer film 5... Field oxide film, 6... Gate oxide film, 7... Field oxide film and gate oxide film joint of. Figure 112

Claims (1)

[Claims] A high-voltage P-channel transistor of a high-voltage MOSIC includes a step of simultaneously forming a field oxide film and a gate oxide film, and a step of removing the oxide film at the gate portion leaving only a predetermined thickness. A method for manufacturing a featured semiconductor device.