A method for manufacturing a capacitor of a semiconductor device includes forming a lower metal layer over a substrate, forming a dielectric layer over the lower metal layer, forming an upper metal layer over the dielectric layer, forming an upper electrode and a dielectric layer pattern by performing a reactive ion etching process with respect to the upper metal layer using the dielectric layer as an etch stop layer, and exposing a top surface of the lower metal layer, and performing a chemical down-stream etch (CDE) process to remove a by-product of a sidewall of the upper electrode.