A hemispherical grain (HSG) formation process for enlarging the surface area of a capacitor electrode, wherein stable, defect-free HSG, having outstanding selectivity, is formed. An amorphous silicon layer, which constitutes a capacitor electrode, is formed on an Si wafer, on which is formed a silicon-based dielectric layer, which constitutes an interlevel dielectric layer. An HSG layer, in which there exists practically no defects, is formed on the amorphous silicon layer at a crystal nuclei formation temperature of under 620 C. Further, in accordance with properly controlling the crystal nuclei formation temperature, and the flow rate of monosilane (SiH₄), which is supplied for crystal nuclei formation, it is possible to furnish selectivity such that HSG nuclei are formed solely on the amorphous silicon layer, without being formed on a silicon-based dielectric layer.