Patent ID: 7510981

Claim:
A method for manufacturing a semiconductor device, comprising: providing a predetermined pattern of a silicon nitride film and an amorphous carbon protective film which covers the silicon nitride film on a silicon semiconductor substrate; selectively etching the semiconductor substrate using said amorphous carbon protective film as a mask to form a trenched portion, the trenched portion being formed via an etch process using an etchant gas under a condition in which an etch selectivity is represented by a ratio: (an etch rate of said silicon semiconductor substrate)/(an etch rate of said amorphous carbon protective film) is equal to or higher than 5; removing said amorphous carbon protective film to expose said silicon nitride film; depositing an element isolation film so as to fill said trenched portion therewith and cover said silicon nitride film; removing the element isolation film formed on said silicon nitride film by polishing thereof until said silicon nitride film is exposed; and removing said silicon nitride film.