PURPOSE: To increase a ratio of electrostatic capacity to an occupation area of a capacity element by deteriorating flatness of a surface of a lower side electrode film, by producing etching residue by anisotropic etching of a surface part of an electrode film and by forming a deep groove in the lower side electrode film through anisotropic etching using the etching residue as a mask.

CONSTITUTION: A thin polycrystalline silicon film 13 is formed on a surface of a polycrystalline silicon film 11 which becomes a lower side electrode film through a thin high concentration PSG film 12 to lower flatness of a surface. Anisotropic etching is carried out on a surface of the polycrystalline silicon film 11 whose surface flatness is lowered under proper etching conditions, thereby dotting with etching residues 14, 14.... Deep grooves 15, 15... are formed in the polycrystalline silicon film 11 by etching the polycrystalline silicon film 11 using the etching residue 14 as a mask to enlarge the surface area of the polycrystalline film 11. The polycrystalline silicon film 11 having an enlarged surface area is used as a lower side electrode film of information storage capacitor element. A dielectric film 16 is formed on a surface of the lower side electrode film and is opposed to an upper side electrode film 17 through the dielectric film 16. Thereby, a capacity element of a large ratio of electrostatic capacity to an occupation area can be acquired.