A storage electrode has a truncated-conical “pipe-shaped” top section having a small inner diameter, mounted on a cylindrical base section having a large inner diameter. To fabricate the storage electrode, a buried contact plug is formed on a first insulating layer on a wafer, and an etching stop layer and a second insulating layer are formed on the first insulating layer. A third insulating layer is formed on the second insulating layer after implanting impurities into the second insulating layer. An opening is formed by anisotropically etching the third insulating layer and the second insulating layer using a photoresist pattern as an etching mask. A cleaning process is carried out such that the second insulating layer exposed through the opening is isotropically etched. After depositing polysilicon along a profile of the second and third insulating layers to a uniform thickness, the remaining third and second insulating layers are removed.