Patent ID: 7244643

Claim:
A semiconductor device comprising: a field region in which an insulative film is buried to the inside of a trench formed to the main surface of a semiconductor substrate; and a plurality of active regions adjacent to the field region, the active regions having a first active region formed with an n-type field effect transistor and a second active region formed with a p-type field effect transistor; wherein: an oxidation preventive film for suppressing oxidation of the semiconductor substrate in the trench is disposed on a lateral surface of the trench in the field region adjacent to the first active region on a side of the first active region which is located in a direction of connecting a source and a drain of the n-type field effect transistor; the oxidation preventive film is not disposed on the lateral surface of the trench in the field region adjacent to the second active region which is located in a direction of connecting a source and a drain of the p-type field effect transistor and the oxidation preventive film for suppressing the oxidation of the semiconductor substrate in the trench is disposed on the lateral surface of the trench in the field region adjacent to the second active region which is located in a longitudinal direction of a gate electrode located between the source and the drain of the p-type field effect transistor.