Methods for forming a mold for a storage electrode in a semiconductor device include forming an interlayer dielectric layer including a contact plug on a substrate. A first mold dielectric layer is formed of a first material on the interlayer dielectric layer. A second mold dielectric layer is formed of a second material on the first mold dielectric layer. The second material has a different etch selectivity than the first material. A first opening is formed that penetrates the first and second mold dielectric layers. The first opening is dry etched to define a second opening having a larger width in the first mold dielectric layer than in the second mold dielectric layer based on the different etch selectivity of the first and second mold dielectric layers to define the mold for the storage electrode.