Method of forming gate dielectric films for MOSFETs without generation of natural oxide films

摘要

In a method of forming gate dielectric films, a surface of a Si wafer is first cleaned in an inert gas ambient into a clean state having no naturally oxidized films. Then, after replacing the inert gas ambient with an oxidizing gas containing no nitrogen without exposing the wafer to air, the wafer is heated in the replaced ambient to form a first silicon oxide film on the silicon surface. Then, the ambient is again replaced with an oxidizing gas containing nitrogen, and the wafer is heated in the replaced ambient to form a first oxynitride film between the first silicon oxide film and the silicon. Thereafter, re-oxidation of the wafer is performed in an ambient of oxidizing gas containing no nitrogen to form a second silicon oxide film between the first oxynitride film and the silicon.