A method of forming a capacitor structure includes forming a mold layer on a substrate, in which the substrate includes a plurality of plugs therein, partially removing the mold layer to form a plurality of openings, in which the plugs are exposed by the openings, forming a plurality of lower electrodes filling the openings, in which the lower electrodes have a pillar shape, removing an upper portion of the mold layer to expose upper portions of the lower electrodes, forming a supporting pattern on exposed upper sidewalls of the lower electrodes and on the mold layer, removing the mold layer, and sequentially forming a dielectric layer and an upper electrode on the lower electrodes and the supporting pattern.