Patent ID: 7166538

Claim:
A method for fabricating a semiconductor device comprising the steps of: forming a gate insulating film on a semiconductor substrate; depositing a silicon film on said gate insulating film; depositing a high-melting point metal film on said silicon film; forming a hard mask made of a silicon oxide film or a silicon nitride film on said high-melting point metal film; dry etching said high-melting point metal film with said hard mask used as a mask; removing a residue or a natural oxide film present on said silicon film through dry etching; and dry etching said silicon film with said hard mask used as a mask, wherein the silicon film before the step of removing a residue or a natural oxide film is a polysilicon film, and the step of removing a residue or a natural oxide film is performed using a mixed gas in which a gas including chlorine and an HBr gas are mixed together while suppressing a difference between an etching rate in a grain boundary of the polysilicon film and an etching rate in the other portion of the polysilicon film and a formation of a groove in the grain boundary of the polysilicon film.