SEMICONDUCTOR DEVICE AND ITS MANUFACTURE

PROBLEM TO BE SOLVED: To prevent a trench oxide film from being etched unexpectedly due to the elimination of a nitride film on the surface of the trench oxide film, and hence to prevent element characteristics from deteriorating when eliminating the nitride film of the bottom part of a connection hole in self-align contact(SAC) structure using the nitride film as an etching stopper. SOLUTION: Nitride films 9, 9a, and 9b are formed by thermal nitriding treatment in ammonium or N2 O atmosphere. Since the diffusion speed of ammonium or N2 O is slower on the surface of a silicon substrate 1 than on the surface of the nitriding films, the nitriding film 9b on the surface of the silicon substrate 1 has a smaller film thickness than that of the nitriding films 9 and 9a on the surface of the nitriding films, thus selectively eliminating only the nitriding film 9b at the bottom part of a connection hole 13, and hence securely preventing the trench oxide film 3 from being etched unexpectedly since the nitriding film 9a on the surface of the trench oxide film 3 cannot be eliminated completely.