The present application discloses a method for fabricating a semiconductor device with a pad structure. The method includes providing a substrate, forming a capacitor structure above the substrate, forming a plurality of passivation layers above the capacitor structure, forming a pad opening in the plurality of passivation layers, performing a passivation process comprising soaking the pad opening in a precursor, and forming a pad structure in the pad opening. The precursor is dimethylaminotrimethylsilane or tetramethylsilane. Forming the pad structure in the pad opening comprises forming a pad bottom conductive layer comprising nickel in the pad opening and forming a pad top conductive layer on the pad bottom conductive layer. The pad top conductive layer comprises palladium, cobalt, or a combination thereof.