Semiconductor device having a thermal nitride film and manufacturing method thereof.

摘要

A semiconductor wafer (31) having an impurity diffusion layer formed in an inner surface of a trench (33) is cleaned. The semiconductor wafer (31) 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 DEG C to 1200 DEG C and the partial pressures of H2O and O2 are set at 1 x 10<-><4> Torr or less. A natural oxide film formed on the inner surface of the trench (33) is removed, and substantially at the same time, a thermal nitride film (35) is formed on the impurity diffusion layer. Then, a CVD silicon nitride film (36) 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 (37) 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 (39) for the composite insulative film is formed in the trench.