High density plasma etching of polysilicon thin films was carried out in an inductively coupled plasma (ICP) for the formation of nanometer-sized patterns. The etch rate and etch selectivity of polysilicon films were investigated as a function of the concentration of Cl₂ and HBr etch gases. The fast etch rate of polysilicon films was obtained in Cl₂/Ar gas, and the high selectivity of polysilicon to photoresist was found in HBr/Ar gas. Finally, the etching of polysilicon films masked with photoresists was attempted in HBr/Ar and Cl₂/Ar gases. The good pattern profile of polysilicon films with 60 nm lines was achieved in an HBr/Ar plasma.