Abstract: A material and method for bonding a semiconductor device to a pedestal, which can obtain a sufficient bonding strength and stable electric contact, are disclosed. On an n-type electrode constituting an ohmic electrode for a semiconductor laser device are formed a Ni layer and an Au-Sn solder layer. Then, the solder layer is melted and bonded to a heat sink provided with Au-plating. The film thickness of the Ni layer is set to approximately 500 .ANG. or more. When the solder layer is melted, Ni in the Ni layer diffuses into the solder layer and Sn in the solder layer diffuses into the Ni layer. By this mutual diffusion, bonding strength and wettability between the semiconductor device and pedestal can be improved. In addition, by setting the composition ratio of Ni layer to the Au-Sn solder layer to 1.3 wt % or more and under 10 wt %, bonding can be performed at a lower melting point and concurrently a higher bonding strength can be obtained.