Patent ID: 6987069

Claim:
A method for fabricating a semiconductor integrated circuit device, comprising the steps of: (a) exposing a first major surface of a wafer to a hydrogen gas atmosphere in a heat treatment chamber; (b) synthesizing moisture, in a first temperature range, not higher than a first temperature, from oxygen gas and hydrogen gas containing more hydrogen than the molar ratio at which the moisture is formed, by use of a catalyst in a moisture synthesizing portion, to produce synthesized moisture; (c) transferring the synthesized moisture together with said more hydrogen into the heat treatment chamber, to form a wet oxidative atmosphere over the first major surface of the wafer inside the chamber, while keeping the moisture in a gaseous state; and (d) performing selective oxidation treatment of a first member over the first major surface of the wafer, in the wet oxidative atmosphere in the heat treatment chamber, by heating the first major surface of the wafer up to a second temperature range not lower than a second temperature higher than the first temperature.