Abstract: A semiconductor laser device of the present invention includes: a semiconductor laser chip including an anode and a cathode; and a field effect transistor. The anode of the semiconductor laser chip is connected to the drain of the field effect transistor. The gate of the field effect transistor is connected to the drain of the field effect transistor. And the cathode of the semiconductor laser chip is connected to the source of the field effect transistor.

Abstract: A semiconductor laser element which is composed of a compound semiconductor consisting of GaAs or the like, a silicon laser mount which is disposed beneath the semiconductor laser element so as to position the element, and on which an electrode layer as an electrode for the semiconductor laser element is formed, a heat sink which is disposed beneath the laser mount so as to dissipate, through the laser mount, the heat generated by the semiconductor laser element are mutually secured through hot contact bonding. The laser mount has a concave portion on the side opposite to its main surface on which the semiconductor layer element is secured, and the concave portion contains a heat dissipating body which is integrated thereinto and is made of copper having higher thermal conductivity than silicon.