Fabrication process of a semiconductor integrated circuit device

A method for fabricating a semiconductor integrated circuit device, comprising the steps of:

• (a) synthesizing moisture in a first temperature range, not higher than a first temperature, from oxygen gas and hydrogen gas by use of a catalyst in a moisture synthesizing portion, to produce synthesized moisture;
• (b) transferring the synthesized moisture into a heat treatment chamber, to form a wet oxidative atmosphere over a first major surface of a wafer inside the chamber, while keeping the moisture in a gaseous state;
• and
• (c) 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,
• wherein step (a) comprises the substeps of;
• (i) introducing hydrogen gas into the moisture synthesizing portion during a first time period;
• and
• (ii) continued from substep (i), introducing oxygen gas and hydrogen gas into the moisture synthesizing portion, thereby synthesizing moisture.

A method for fabricating a semiconductor integrated circuit device, comprising the steps of:

• (a) synthesizing moisture in a first temperature range, not higher than a first temperature, from oxygen gas and hydrogen gas by use of a catalyst in a moisture synthesizing portion, to provide synthesized moisture;
• (b) transferring the synthesized moisture into a heat treatment chamber, to form a wet oxidative atmosphere over a first major surface of a wafer inside the chamber, while keeping the moisture in a gaseous state;
• and
• (c) 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 in a second temperature range not lower than a second temperature higher than the first temperature, wherein introduction of the oxygen gas, used for forming moisture, into the moisture synthesizing portion, is not started prior to the start of introduction of the hydrogen gas into the moisture synthesizing portion.