A method of forming a cylindrical lower electrode of a capacitor in which metal is used as a lower electrode of a capacitor. A metal capping layer is used in order to protect the inner walls of the cylindrical metal lower electrode. A sacrificial insulating layer is patterned to form an aperture for forming the lower electrode. A metal lower electrode layer and the metal capping layer are sequentially formed. In order to electrically separate adjacent metal lower electrodes from each other, the metal capping layer and the metal lower electrode layer are simultaneously planarized until the sacrificial insulating layer is exposed. The sacrificial insulating layer and the metal capping layer that resides in the aperture are removed such that the cylindrical metal lower electrode having inner and outer walls is completed. Therefore, it is possible to simultaneously palanarize the metal capping layer and the metal lower electrode layer with respect to the sacrificial insulating layer such that it is possible to simplify processes for forming the lower electrodes.