Patent ID: 8728903

Claim:
A method of manufacturing a semiconductor device, comprising: forming a film functioning as a gate insulating film and a film functioning as a gate electrode on a semiconductor substrate; removing the film functioning as a gate electrode, the film functioning as a gate insulating film and the semiconductor substrate to form a first isolation trench and a second isolation trench, and forming a first element region, a first gate insulating film and a first gate electrode, which are isolated via the first isolation trench, and forming a second element region, a second gate insulating film and a second gate electrode, which are isolated via the second isolation trench; and forming a first oxide film on a sidewall of the first element region while forming a second oxide film on a sidewall of the second element region in an atmosphere containing radical oxygen, wherein a top portion of the first isolation trench has a width narrower than a top portion of the second isolation trench, and the first oxide film has a thickness thinner than the second oxide film.