A method for forming a capacitor of a semiconductor device includes forming a cylindrical storage node over a semiconductor substrate; depositing a first dielectric layer over the cylindrical storage node; and etching the first dielectric layer to reduce a thickness of a portion of the first dielectric layer on a protruded end of the cylindrical storage node. The method further includes depositing a second dielectric layer over the etched first dielectric layer, wherein the second dielectric layer supplements a thickness of a portion of the first dielectric layer on a bottom corner of the cylindrical storage node. Finally, a cell plate is formed over the second dielectric layer.