A semiconductor device is provided in which a semiconductor chip is bonded to a substrate with a sufficiently increased bonding strength and cracking is assuredly prevented which may otherwise occur due to heat shock, heat cycle and the like. The semiconductor device includes a semiconductor chip and a substrate having a bonding area to which the semiconductor chip is bonded via a metal layer. The metal layer includes an Au—Sn—Ni alloy layer and a solder layer provided on the Au—Sn—Ni alloy layer. Undulations are formed in an interface between the Au—Sn—Ni alloy layer and the solder layer.