Provided is a capacitor of a semiconductor device and a method of fabricating the same. In one embodiment, the capacitor includes a lower electrode formed on a semiconductor substrate; a dielectric layer formed on the lower electrode; and an upper electrode that is formed on the dielectric layer. The upper electrode includes a first conductive layer, a second conductive layer, and a third conductive layer stacked sequentially. The first conductive layer comprises a metal layer, a conductive metal oxide layer, a conductive metal nitride layer, or a conductive metal oxynitride layer. The second conductive layer comprises a doped polysilicon germanium layer. The third conductive layer comprises a material having a lower resistance than that of the second conductive layer.