High density plasma etching of polysilicon thin films with nanometer-size patterns was performed in an inductively coupled plasma. The etch process of polysilicon films with a photoresist mask was characterized using Cl-2, C2F6, and HBr gas chemistries in terms of etch rate, etch selectivity, and etch profile. The fast etch rate of polysilicon films was obtained in Cl-2/Ar gas and the high selectivity of polysilicon to photoresist was found in HBr/Ar gas mixture. The etching of polysilicon films masked by photoresist with nanometer-size patterns was attempted with various etch gases, and an anisotropic etching of 60 nm sized pattern was achieved in HBr/Ar and C2F6/Ar plasmas. (C) 2003 The Electrochemical Society.