having the hemispherical grains as well as micro recesses smaller in size than the semi spherical grains as shown in fig2 c and the surface area of the porous silicon film 93a is twice larger than the lower electrode covered with hemispherical grains only and four times lager than the ordinary polysilicon surface as shown in fig2 in fig2 plots pl1 pl2 pl3 and pl4 respectively stand for an ordinary stacked type lower electrode without any treatment a stacked type lower electrode with micro recesses a stacked type lower electrode with hemispherical grains and a stacked type lower electrode with micro recesses in hemispherical grains finally a composite dielectric layer 94 covers the porous silicon film 93a and an upper electrode 95 is patterned from a doped polysilicon film as shown in fig2 d although the composite dielectric layer 94 forms the upper surface over the rugged surface in fig2 d the composite polysilicon layer 94 conformally extends and forms secondary micro recesses and the doped polysilicon fills the secondary micro recesses in this instance the phosphorous atoms are introduced through diffusion however impurities atoms may be ion implanted into the hemispherical grains or an in site doping technology may be employed for the amorphous silicon film moreover arsenic atoms may be introduced instead of the phosphorus atoms even if a lower electrode is formed of amorphous silicon phosphoric acid perforates the lower electrode for example a doped amorphous silicon.