After an interlayer insulating film is deposited on a silicon substrate, a contact hole or contact holes is or are formed at a desired position(s) and, then, after a polysilicon layer is deposited and the contact hole(s) is (are) embedded, the surface of the polysilicon layer is flattened by chemical and mechanical polishing using at least one of piperazine or colloidal silica slurry, and a barrier metal film 4 and a highly dielectric thin film 5 are deposited and processed to a desired size. Finally, an Al/TiN film 6 adapted for the upper electrode is formed. The leak current of the thin film capacitor which is obtained according to this method can be greatly reduced.