| 摘要 |
A memory transistor and a high breakdown voltage MOS transistor are easily formed on the same semiconductor substrate without changing the operational characteristics of the memory transistor. The process of forming the tunnel insulation film of the memory transistor and the process of forming the gate insulation film of the MOS transistor are performed separately. Concretely, an insulation film to be a part of the tunnel insulation film and a silicon nitride film are formed on the whole surface, and then the silicon nitride film in a MOS transistor formation region is selectively removed using a photoresist layer. Then, the MOS transistor formation region is selectively oxidized using the remaining silicon nitride film as an anti-oxidation mask to form the gate insulation film of the MOS transistor having a selected thickness. |
