Method for fabricating semiconductor device

Abstract

A mask (4) for forming active regions is formed on a surface portion of a Si layer (2) serving as a semiconductor region with a thermal oxide film (3) interposed therebetween. Dummy sidewalls (8) are formed over the side surfaces of the mask (4) for forming active regions. Then, etching is performed by using the mask (4) for forming active regions and the dummy sidewalls (8) as a mask to form trenches (9) each defining the side surfaces of the Si layer (2). Thereafter, each of the trenches (9) is filled with a plasma CVD oxide film (11), which is polished till the dummy sidewalls (8) are exposed at the surface. By removing the dummy sidewalls (8), oxidation is performed with the upper-surface edge portions of the Si layer (2) being exposed. This allows the upper-surface edge portions of the Si layer (2) to be oxidized without involving the oxidation of the lower-surface edge portions of the Si layer (2).

Dependencies are inferred from the claim text.