Patent ID: 7683455

Claim:
A semiconductor device comprising: a semiconductor substrate having a trench at a main surface thereof; an oxidation preventive film including a nitrogen formed along an inner wall and a bottom surface of said trench; a filling layer filling said trench with said preventive film located between said filling layer and said semiconductor substrate; a gate oxide film formed on said main surface of said semiconductor substrate and said oxidation preventive film; and a gate electrode formed on said gate oxide film, wherein said gate oxide film has substantially the same thickness in a region directly above said oxidation preventive film and a region directly below said gate electrode and said gate oxide film directly above said oxidation prevention film includes said nitrogen, wherein said gate oxide film is made according to a method comprising the step of applying a high oxidation capability on said main surface of a semiconductor substrate in an atmosphere in which radicals of at least one kind of hydrogen radicals and at least one kind of oxygen radicals are generated to thereby oxidize an upper surface of the oxidation preventive film and said main surface of said semiconductor substrate.