Patent ID: 7642172

Claim:
A method comprising: forming trenches in a semiconductor substrate; forming an oxide film over the side surfaces and bottom surface of the trenches by thermal oxidation; depositing a first liner silicon nitride film over the entire surface of the semiconductor substrate including the trenches; sequentially depositing an oxide film on the first liner silicon nitride film and a second liner silicon nitride film on the oxide film; removing the second liner silicon nitride film and the oxide film in predetermined one of the trenches by anisotropy etching and isotropy etching; depositing a dielectric filler over the entire surface of the semiconductor substrate including the trenches; removing portions of the dielectric filler over the uppermost surface of the semiconductor substrate; and forming a first device isolation having a multi-layered liner silicon nitride film in first ones of the trenches and a second device isolation layer having the first liner silicon nitride film formed in other ones of the trenches by etching portions of the first liner silicon nitride film, the second liner silicon nitride film and the oxide film formed over the uppermost surface of the semiconductor substrate.