Method of fabricating semiconductor device without having grooves at edge portions of STI

A method for fabricating a semiconductor device, comprising the steps of:

• sequentially forming a pad oxide film, a polysilicon film, and an antioxidation film on an active region of a semiconductor substrate such that a field region is exposed, wherein the polysilicon film is formed with a dual stacked structure of a doped polysilicon film and an undoped polysilicon film;
• etching an exposed portion of the surface of the substrate to a predetermined thickness to form a trench within the substrate;
• forming a first insulation film along an inner face of the trench by using an oxidation process to form a resultant structure;
• forming a stress buffer film on the entire surface of the resultant structure;
• forming a second insulation film on the stress buffer film such that the trench is substantially filled;
• making planar the second insulation film such that the antioxidation film remains with a predetermined thickness on the active region of the substrate so as to form a shallow trench isolation within the trench;
• and
• sequentially removing the remaining antioxidation film, the polysilicon film, and the pad oxide film.