Patent ID: 6939810
Filing Date: 2005-09-06
Classification: H01L

Abstract:
1. A method of forming an isolation film, comprising the steps of: forming a first silicon oxide film on a semiconductor substrate; forming a silicon nitride film on said first silicon oxide film; performing patterning to said silicon nitride film; etching said first silicon oxide film and said semiconductor substrate using said silicon nitride film as a mask and forming trenches severally in a first region and a second region of said semiconductor substrate; a first isotropic etching in which isotropic etching is performed to said silicon nitride film; a second isotropic etching in which said first region is protected by a first resist film and isotropic etching is performed to said silicon nitride film in said second region; removing said first resist film; depositing silicon oxide over the entire upper surface of said semiconductor substrate and forming a second silicon oxide film; removing said second silicon oxide film until said silicon nitride film exposes; removing said silicon nitride film; oxidizing the surface of said semiconductor substrate and forming a third silicon oxide film; a third isotropic etching in which said third silicon oxide film is removed and performing isotropic etching to said remaining second silicon oxide film; oxidizing the surface of said semiconductor substrate and forming a fourth silicon oxide film; a fourth isotropic etching in which said first region is protected by a second resist film, said fourth silicon oxide film in said second region is removed, and isotropic etching is performed to said second oxide film in said second region; removing said second resist film; and oxidizing the surface of said semiconductor substrate and forming a fifth silicon oxide film.