Nanometer-sized patterning of polysilicon thin films was performed by a high density inductively coupled plasma (ICP) etching. The etch characteristics of polysilicon thin films with an e-beam resist mask were investigated using Cl-2, C2F6, and HBr-based gas mixes. The etch rate, the etch selectivity and the etch profile of polysilicon films were examined as a function of the concentration of each gas, using Ar as a diluent. The Cl-2 gas showed fast etch rate of polysilicon films, and the high selectivity of polysilicon films to resist was obtained in HBr and C2F6 gases. The effect of an etch gas on the etch profile of polysilicon thin films was observed using field emission scanning electron microscopy for nanometer-sized patterns. Good nanometer-sized patterning of polysilicon thin films with 60 and 95 nin wide lines has been achieved in HBr/Ar and C2F6/Ar plasmas. (C) 2004 Elsevier B.V. All rights reserved.