A semiconductor device may include a bottom sub-electrode on a substrate, a top sub-electrode on the bottom sub-electrode, a dielectric layer covering the bottom and top sub-electrodes, and a plate electrode on the dielectric layer. The top sub-electrode may include a step extending from a side surface thereof, which is adjacent to the bottom sub-electrode, to an inner portion of the top sub-electrode. The top sub-electrode may include a lower portion at a level that is lower than the step and an upper portion at a level which is higher than the step. A maximum width of the lower portion may be narrower than a minimum width of the upper portion. The maximum width of the lower portion may be narrower than a width of a top end of the bottom sub-electrode. The bottom sub-electrode may include a recess in a region adjacent to the top sub-electrode.