A semiconductor device having nickel suicide and a method for fabricating nickel silicide. A semiconductor substrate having a plurality of doped regions is provided. Subsequently, a nickel layer is formed on the semiconductor substrate, and a first rapid thermal process (RTP) is performed to react the nickel layer with the doped regions disposed thereunder. Thereafter, the unreacted nickel layer is removed, and a second rapid thermal process is performed to form a semiconductor device having nickel silicide. The second rapid thermal process is a spike anneal process whose process temperature is between 400 and 600° C.