Method of manufacturing semiconductor device isolation region

摘要

The present invention aims to prevent formation of a bird's beak and a bird's head in forming a miniaturized element isolation oxide film, and to suppress introduction of a defect into a silicon substrate. A first silicon oxide film is formed on the surface of a silicon substrate. A polycrystalline silicon film and a first silicon nitride film having an opening are formed on surface of the first silicon oxide film. A second silicon oxide film is deposited on the surface of the first silicon oxide film and the first silicon nitride film so as to cover the inner wall of the opening by a CVD method. A second silicon nitride film formed to cover the surface of the second silicon oxide film is subjected to anisotropical etching, whereby a sidewall nitride film is formed on the surface of the second silicon oxide film so as to cover the sidewall of the opening. With the sidewall nitride film as a mask, an element isolation film is formed at the bottom of the opening.