Patent ID: 7303951

Claim:
A method of manufacturing a semiconductor device comprising the steps of: (a) forming a silicon nitride film by way of a first silicon oxide film over the main surface of a silicon substrate; (b) forming a second silicon oxide film over the silicon nitride film, and then forming a photoresist film in which a element isolation region is opened over the second silicon oxide film; (c) applying a wet etching treatment to the second silicon oxide film, exposed through the photoresist film, in the element isolation region, after the step (b); (d) dry etching the silicon nitride film and the first silicon oxide film by using the photoresist film as a mask after the step (c), thereby exposing the silicon substrate in the element isolation region; (e) removing the photoresist film; (f) dry etching the silicon substrate by using the silicon nitride film as a mask after the step (e), thereby forming a trench in the silicon substrate in the element isolation region; (g) forming a third silicon oxide film over the silicon substrate including the inside of the trench, then removing the third silicon oxide film outside the trench by a chemical mechanical polishing method, or a chemical mechanical polishing method followed by etching back, to leave the third silicon oxide film inside the trench, thereby forming an element isolation trench in the silicon substrate in the element isolation region; and (h) removing the silicon nitride film.