A method of forming a capacitor for a semiconductor device is disclosed. According to the method, a silicon germanium layer and an oxide layer are used as mold layers for forming a storage electrode. The oxide layer and the silicon germanium layer are anisotropically etched to form an opening and then the silicon germanium layer is further isotropically etched to form a recessed portion of the opening, such that the recessed portion of the opening formed in the silicon germanium layer is wider than at least some portion of the opening through the oxide layer. Thus, the mold layers are used to form a storage electrode having a lower portion which is wider than an upper portion thereof.