PURPOSE: To obtain a semiconductor laser, provided with a refractive index waveguide structure, which can be manufactured by a single process.

CONSTITUTION: In the semiconductor laser in which an active layer 3 is pinched by the upper and lower two clads layers 2 and 4 which are formed in a semiconductor layer substrate, the ions which make a grating constant a little larger than the clad layer 2 are implanted into the part corresponding to the center part of the active layer 3 of the clad layer 2, an active layer 3 is grown on the upper surface of the clad layer 2, and a refractive index waveguide structure is formed.