To form a uniform and high quality silicon oxide film on a substrate surface at a low substrate temperature of 200-500 degrees and to provide a semiconductor device using the silicon oxide film in which a thickness of the silicon oxide film on a silicon surface on a sidewall part of a recess portion of an element isolation region is reduced to 30% or less thereby improving device reliability.

A silicon oxide film contains Kr. By containing Kr in the silicon oxide film to ease stress occurring in the silicon oxide film and at a silicon/silicon oxide film interface, a high quality silicon oxide film is formed although formed at a low temperature. Uniformity of a thickness of the silicon oxide film on a silicon surface on a sidewall part of a recess portion of an element isolation region is reduced to 30% or less.