PURPOSE: To increase the degree of freedom of the direction of a heat sink in case of assembling the heat sink and improve the workability by forming metal films isolated from each other on the opposed second surfaces on the first surface of a substrate, and disposing grooved recesses on the surface and symmetrically to both side surfaces.

CONSTITUTION: A gold film 24 is formed through a titanium film 22 and a platinum film 23 on both side surface of a substrate 21 made of a silicon single crystal, and L-shaped grooved recesses 25 selectively removed, for example, on the film 24 are formd symmetrically on both upper and lower surfaces. A laser chip 1 is bonded on a heat sink via melting metal material 26, the material 26 is prevented from spreading via the recess 26 spreading on the upper surface of the film 25, and the bonding region of wirings 16 is obtained. Assembling can be performed without limit in the direction entirely the same as the heat sink formed with uniform metal films on the entire upper and lower surfaces.