Method of etching polycrystalline silicon film by using two consecutive dry-etching processes

摘要

A method for fabricating a semiconductor device including the steps of: sequentially forming an oxide film and a polycrystalline silicon film overlying a substrate; and selectively dry-etching the polycrystalline silicon film in consecutive two processes including a main etching process for dry-etching the polycrystalline silicon film under existence of Cl₂, HBr and CF₄ and an over-etching process for dry-etching the polycrystalline silicon film under existence of HBr and oxygen. In the process, the polycrystalline silicon film is etched in the main etching process with the excellent dimension controllability and is etched in the over etching process with the higher selective ratio between the polycrystalline silicon film and the gate oxide film.