SEMICONDUCTOR DEVICE

PURPOSE:To improve productivity while obtaining a device, cost of which is reduced, by introducing laser beams for monitoring from a laser diode to a light-receiving element by using a reflecting surface. CONSTITUTION:A laser diode 1, which emits laser beams in at least two directions and one laser beams of which are employed as laser beams 20 for monitor, and a reflecting surface 11 reflecting laser beams 20 for monitor from the laser diode 1 and introducing them to a light-receiving element 4 are mounted. The laser diode 1 and the light-receiving element 4 are fixed onto the same plane of a substrate 10 formed by SiC, AlN, etc. having high thermal conductivity. The laser diode 1 is arranged so as to emit laser beams 21, 20 in the vertical direction in the figure, the light-receiving element 4 is disposed on the outgoing direction side of laser beams 20 for monitoring the laser diode 1, and a reflecting surface 11a is allowed to face the light-receiving surface 4a at a fixed inclination and the reflecting plate 11 is fastened onto the substrate 10.