Abstract: According to the present invention, to flatten the surface of a silicon substrate by polishing an element isolating buried insulation film by chemical mechanical polishing, a polysilicon film is formed on the top surface of a projection of a silicon substrate. After that, a buried insulation film is formed all over the silicon substrate along the irregularities thereof. A carbon film is formed on the surface of a recess of the buried insulation film. Using the carbon film as a stopper, the buried insulation film is polished by the chemical mechanical polishing to ease the irregularities of the surface of the polished insulation film. Then the carbon film is removed and, using the polysilicon film as a stopper, the buried insulation film is polished by the chemical mechanical polishing to flatten the surface of the polished insulation film. Thus, the flatness of the buried insulation film can easily be controlled, and the surface of the silicon substrate can always be flattened satisfactorily.

Abstract: For providing different conductivity type contact electrodes being in contact with different conductivity type semiconductor regions formed in a semiconductor substrate, after an insulating film is formed on the semiconductor substrate, it is selectively etched down to one conductivity type semiconductor region to provide a first contact hole therein. One conductivity type doped polysilicon layer is deposited over the substrate surface to fill the first contact hole therewith. Thereafter, the one conductivity type doped polysilicon layer and the insulating film are selectively removed down to an opposite conductivity type semiconductor region to provide a second contact hole therein. An opposite conductivity type doped polysilicon layer is deposited over the substrate surface to fill the second contact hole therewith. These polysilicon layers are then removed from the surface of the insulating film to provide first and second contact electrodes in the contact holes.