Patent ID: 7402473

Claim:
A process for producing a semiconductor device, comprising: forming a first oxide film on a semiconductor substrate by a first oxidizing process of the semiconductor substrate, forming a silicon nitride film on the first oxide film, forming a photoresist film on the silicon nitride film, removing a portion of the photoresist film, removing the silicon nitride film and the first oxide film at the removed portion of the photoresist film, trenching a groove at an angle of 95° to 110° of the inside wall of the groove to the surface of the semiconductor substrate in an element isolation region in a portion of the semiconductor substrate from which the first oxide film is removed, removing another portion of the photoresist film on the silicon nitride film, forming a recessed space under the silicon nitride film by etching the first oxide film from the region where the groove is formed, forming a second oxide film in the recessed space by thermally oxidizing the semiconductor substrate to a degree not greater than the amount of oxidation that develops upward warping deformation of the silicon nitride film, and embedding a third oxide film in the groove, removing the silicon nitride film and the first oxide film on the semiconductor substrate, and forming a gate dielectric film and a gate electrode on the semiconductor substrate.