A method for manufacturing capacitor lower electrodes includes a dielectric layer, a first silicon nitride layer and a hard mask layer; partially etching the hard mask layer, the first silicon nitride layer and the dielectric layer to form a plurality of concave portions; depositing a second silicon nitride layer onto the hard mask layer and into the concave portions; partially etching the second silicon nitride layer, the hard mask layer and the dielectric layer to form a plurality of trenches; forming a capacitor lower electrode within each trench and partially etching the first silicon nitride layer, the second silicon nitride layer, the dielectric layer and the capacitor lower electrodes to form an etching area; and etching and removing the dielectric layer from the etching area, thereby a periphery of each capacitor lower electrode is surrounded and attached to by the second silicon nitride layer.