| 摘要 |
PROBLEM TO BE SOLVED: To obtain a device structure which enhances a gate-insulating-film characteristic and a transistor characteristic in a semiconductor device having the gate of a MOS structure and to obtain its manufacturing method. SOLUTION: This semiconductor device comprises the gate of a MOS structure provided with a laminated gate insulating film which contains at least two kinds of insulating films, i.e., a thermal oxide film 9 formed on a semiconductor substrate and a CVD oxide film 10 formed on the side a gate electrode 11 from the thermal oxide film 9. The ratio of the CVD oxide film 10 is set at 20% or higher of the film thickness of the laminated gate insulating film as a whole. In addition, after the thermal oxide film 9 or the CVD oxide film 10 is formed, a nitriding operation by N2O, NH3 or NO gas is performed, and nitrogen may be segregated in one or both of the interface between the thermal oxide film and the substrate and the interface between the gate electrode and the CVD oxide film. Alternatively, after the thermal oxide film 9 or the CVD oxide film 10 is formed, an Si3N4 film is formed by an LPCVD operation, the surface of the Si3N4 film is oxidized, and an oxide film may be formed.
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