Capacitor forming methods may include sequentially forming a first mold layer, a first support material layer, and a second mold layer on a substrate, forming a mask pattern on the second mold layer, forming a recess in the second mold layer, the first support material layer, and the first mold layer using the mask pattern as a mask, forming a lower electrode in the recess, removing the mask pattern by a dry cleaning process, reducing a width of an upper portion of the lower electrode, removing the first mold layer, forming a dielectric layer on a surface of the lower electrode, and forming an upper electrode on the dielectric layer.