| 摘要 |
For fabricating a semiconductor device having gate oxide films of different film thicknesses and a device isolation oxide film having an elevated device isolation characteristics, an oxidation-resistant film such as a nitride film is formed to cover the whole surface of a semiconductor substrate having a plurality of active regions defined by a device isolation oxide film and covered with a thin oxide film. The oxidation-resistant film and the thin oxide film are removed using, as a mask, a first resist exposing a first device formation area, and after the first resist is removed, a first gate oxide film is formed by thermally oxidizing the whole surface. The oxidation-resistant film and the thin oxide film are removed using, as a mask, a second resist exposing a second device formation area, and after the second resist is removed, a second gate oxide film is formed by thermally oxidizing the whole surface, so that the second gate oxide film is formed on an exposed surface of the substrate in the second device formation area, and the second gate oxide film is formed additionally on the first gate oxide film formed on the substrate surface in the first device formation area. Thus, the substrate surface is covered with the oxidation-resistant film just until a gate oxidation, with the result that since it is possible to prevent an unnecessary oxide film from being formed on the substrate, the etching-removal of the oxide film carried out just until the gate oxidation can be reduced, so that the thinning of the device isolation oxide film can be minimized.
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