PURPOSE: To improve product yield with high productivity by establishing a reliable method for forming a current blocking layer on a stepped surface of a semiconductor substrate by a combination of epitaxial growth and selective etching.

CONSTITUTION: After a step which is extended in parallel with the optical axis of laser beams is formed on an N type semiconductor substrate 1, a P type semiconductor layer 9 which is of lower refractive index than an active layer 3 so as to serve as current blocking layer 9 is formed by epitaxial growth covering the surface to flatten out the stepped surface. After this, a step is formed again on the surface of the substrate 1, extending in parallel with the optical axis of laser beams to produce such a substrate crystal as the semiconductor layer 9 is exposed on the side and also on the lower surface of the stepped surface in addition to part of the substrate 1 being exposed at least on one of the side or the lower surface. Then, an N type semiconductor layer 2, a P type semi conductor layer 4 of lower refractive index than the active layer 3, and an N type semiconductor layer 51 which has a forbidden band gap are grown successively. Type of conductivity of the layer 51 is then made to be P type by striped inversion to form a reflector for a laser resonator at right angle to the extended direction of the step.