A method of fabricating a semiconductor device includes forming a bottom electrode material layer containing aluminum and copper over the substrate. An insulating material layer and a top electrode material layer are sequentially formed on the surface of the bottom electrode material layer. A photoresist pattern is formed on the top electrode material layer, and then the top electrode material layer is patterned to form a top electrode by using the photoresist pattern as mask. The photoresist pattern is removed by plasma ash and then an alloy process is performed to the bottom electrode material layer. Thereafter, the insulating material layer, and the bottom electrode material layer are patterned to form a patterned insulating layer and a patterned bottom electrode layer.