Patent ID: 6995093

Claim:
A polysilicon etching method comprising steps of: preparing a semiconductor substrate having an insulating film with a protrusion formed on one principal surface of said substrate and a polysilicon layer deposited on said insulating film and covering the protrusion; forming a resist layer on the said polysilicon layer, said resist layer having a predetermined pattern not covering at least a portion of side walls of the protrusion; performing a first plasma etching process of etching said polysilicon layer by using mixture gas of HBr and Cl 2 and said resist layer as a mask to leave said polysilicon layer having a pattern corresponding to said resist layer and polysilicon residues made of a portion of said polysilicon layer on the side walls of the protrusion; and performing a second plasma etching process of removing the polysilicon residues by using single gas of HBr and said resist layer as a mask.