barrier metal layer 7 have been removed is used as a mask the silicon nitride 108 is removed with phosphorus acid heated to 150 u00b0 c by which an insulating film 8 is formed since the part from which silicon nitride has been removed is 1 3 u03bcm square which has been obtained by wet etching with phosphorus acid the silicon nitride has been removed isotropically the resulting side wall configuration being bow shaped the method for removing the insulating film is not limited to the one shown in this embodiment and normal photolithography process and dry etching process may also be used only if the side wall portion of the removal part is bow shaped or conical shaped thereafter the mask silicon oxide 109 is removed fig8 next iridium 110 to form the lower electrode is deposited overall to 300 nm by dc magnetron sputtering process fig9 in this case since the side wall of the part from which silicon nitride has been removed is bow shaped the iridium 110 is deposited evenly also to the side wall portion next the iridium 110 is polished by cmp process until the insulating film 8 is exposed so that the iridium 110 and the insulating film 8 become flush with.