SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME

Abstract

A semiconductor device including a high voltage element and a low voltage element, including: a semiconductor substrate having high voltage element region where the high voltage element is formed, and a low voltage element region where the low voltage element is formed; a first LOCOS isolation structure disposed in the high voltage element region; and a second LOCOS isolation structure disposed in the low voltage element region, wherein the first LOCOS isolation structure includes a LOCOS oxide film formed on a surface of the semiconductor substrate and a CVD oxide film formed on the LOCOS oxide film, and the second LOCOS isolation structure includes a LOCOS oxide film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIGS. 2A through 2G show cross sectional views of steps for manufacturing the semiconductor device according to the embodiment 1 of the present invention;

FIGS. 3A through 3D show cross sectional views of other steps for manufacturing the semiconductor device according to the embodiment 1 of the present invention;

FIG. 4 is a cross sectional view of a semiconductor device according to an embodiment 2 of the present invention;

FIGS. 5A through 5C show cross sectional views of steps for manufacturing the semiconductor device according to the embodiment 2 of the present invention;

FIG. 6 is a cross sectional view of a semiconductor device according to an embodiment 3 of the present invention;

FIGS. 7A through 7C show cross sectional views of steps for manufacturing the semiconductor device according to the embodiment 3 of the present invention; and

FIG. 8 is a cross sectional view of a conventional semiconductor device.

Claims

1. A semiconductor device including a high voltage element and a low voltage element, comprising: a semiconductor substrate having high voltage element region where said high voltage element is formed, and a low voltage element region where said low voltage element is formed;a first LOCOS isolation structure disposed in said high voltage element region; anda second LOCOS isolation structure disposed in said low voltage element region, whereinsaid first LOCOS isolation structure includes a LOCOS oxide film formed on a surface of said semiconductor substrate and a CVD oxide film formed on said LOCOS oxide film, andsaid second LOCOS isolation structure includes a LOCOS oxide film.

2. The semiconductor device according to claim 1, wherein the film thickness of said LOCOS oxide film included in said first LOCOS isolation structure is approximately the same as that of said LOCOS oxide film included in said second LOCOS isolation structure.

3. The semiconductor device according to claim 1, wherein said CVD oxide film has a multi-layer structure formed of at least a lower CVD oxide film layer and a upper CVD oxide film layer disposed on said lower CVD oxide film layer, and said CVD oxide film has a stepped edge portion formed of said lower CVD oxide film layer and said upper CVD oxide film layer.

4. The semiconductor device according to claim 3, wherein a field plate is disposed so as to cover said stepped edge portion.

5. The semiconductor device according to claim 1, wherein said second LOCOS isolation structure further includes a CVD oxide film disposed on said LOCOS oxide film.

6. A method of manufacturing a semiconductor device including a high voltage element and a low voltage element, comprising: a step of preparing a semiconductor substrate having a high voltage element region where said high voltage element is formed, and a low voltage element region where said low voltage element is formed;a step of forming LOCOS oxide films on said high voltage element region and said low voltage element region; anda CVD step of forming a CVD oxide film on said LOCOS oxide film in said high voltage element region, thereby forming an isolation structure formed of said LOCOS oxide film and said CVD oxide film.

7. The manufacturing method according to claim 6, further comprising a step of forming a nitrogen film on a surface of said semiconductor substrate before forming said LOCOS oxide film, and wherein said CVD step comprises: a step of forming said CVD oxide film on said nitrogen film;a step of etching said CVD oxide film using a mask formed on said CVD oxide film and leaving said CVD oxide film so that said CVD oxide film overlaps with said nitrogen film at its circumference; anda step of wet-etching said CVD oxide film and removing an overlapping section of said CVD oxide film which overlaps with said nitrogen film.

8. The manufacturing method according to claim 6, wherein said CVD step comprises: a step of forming a lower CVD oxide film layer on said LOCOS oxide film and thermally processing said lower CVD oxide film layer;a step of forming an upper CVD oxide film layer on said lower CVD oxide film layer; anda step of wet-etching said upper CVD oxide film layer and said lower CVD oxide film layer using a mask formed on said upper CVD oxide film layer, and thereby forming said CVD oxide film having a stepped edge portion formed of said upper CVD oxide film layer and said lower CVD oxide film.

9. The manufacturing method according to claim 6, further comprising a step of forming a CVD oxide film on said LOCOS oxide film of said low voltage element region.

10. The manufacturing method according to claim 6, wherein said LOCOS oxide film of said high voltage element region and said LOCOS oxide film of said low voltage element region are formed at the same step.