Patent ID: 7053007

Claim:
A method for fabricating a semiconductor integrated circuit device, comprising the steps of: (a) forming a first silicon oxide film on a first major surface of a wafer in a first wet oxidative atmosphere by thermal oxidation; (b) forming an oxidation barrier film over the first silicon oxide film; (c) patterning an opening in the oxidation barrier film and the first silicon oxide film; (d) forming an isolation groove in the first major surface of the wafer under the opening under the conditions that the patterned oxidation barrier film and the patterned first silicon oxide film exist; (e) forming a second silicon oxide film on an inner surface of the isolation groove in a second wet oxidative atmosphere in a heat treatment chamber by thermal oxidation; (f) after step (e), forming an insulating film over the oxidation barrier film and in the isolation groove; and (g) removing the insulating film outside the isolation groove so as to leave the insulating film inside the isolation groove, wherein the first wet oxidative atmosphere includes moisture synthesized from hydrogen gas and oxygen gas by catalyst.