the impurity doped polysilicon film a silicon nitride film not shown is formed by the cvd method a chemical solution or the like is used to remove a bottom surface of the silicon nitride film and an upper portion of the impurity doped polysilicon film as a result the bit insulating film 3 of a portion where the cell bit contact 4 is to be formed and the bit insulating film 3 of the cavity portion 40 a that faces the above portion are exposed then a titanium nitride film is formed in such a way as to cover the exposed bit insulating film 3 the silicon nitride film that is formed on the bit insulating film 3 and the upper surface of the impurity doped polysilicon film etching back of an upper portion thereof is performed a silicon oxide film is formed in such a way as to be embedded in the cavity portion 40 a and etching back of an upper portion of the silicon oxide film is performed to the extent that the titanium nitride film is not exposed then a mask film that is made of cobalt silicon or the like is formed in such a way as to cover the silicon oxide film formed inside the cavity portion 40 a and the exposed silicon.