| 摘要 |
A semiconductor wafer having an impurity diffusion layer formed in an inner surface of a trench is cleaned. The semiconductor wafer is inserted into a furnace, and NH3 gas is introduced into the furnace in the low-pressure condition to create an atmosphere in which the temperature is set at 800° C. to 1200° C. and the partial pressures of H2O and O2 are set at 1x10-4 Torr or less. A natural oxide film formed on the inner surface of the trench is removed, and substantially at the same time, a thermal nitride film is formed on the impurity diffusion layer. Then, a CVD silicon nitride film is formed on the thermal nitride film without exposing the thermal nitride film to the outside air in the same furnace. Next, a silicon oxide film is formed on the CVD nitride film. As a result, a composite insulative film formed of the thermal nitride film, CVD silicon nitride film and silicon oxide film is obtained. Then, an electrode for the composite insulative film is formed in the trench.
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