To form stable hemispherical grained silicon (HSG) which have superior selectivity and less defects in an HSG forming process which is performed for enlarging the surface areas of capacity electrodes.

On an Si wafer on which a silicon-based insulating film which becomes an interlayer insulating film is formed, an amorphous silicon film which becomes a capacity electrode is formed. Then an HSG film containing few defects is formed on the amorphous silicon film by setting the crystal nucleus forming temperature at <620°C. In addition, when the flow rate of monosilane (SiH4) which is supplied for forming crystal nuclei and the crystal nucleus forming temperature are appropriately controlled, such selectively can be realized that HSG nuclei are not formed in the silicon-based insulating film, but only on the amorphous silicon film.