PURPOSE: To obtain a semiconductor laser having a refractive index waveguide structure wherein a horizontal mode is stable, by making at least one coating layer grow before a high refractive index layer causing an effective refractive index difference is made to grow in a stripe-shaped groove part.

CONSTITUTION: On a clad layer 4 formed on the opposite side of an active layer 3 to a substrate 1, a layer 5 different in a conductivity type from the clad layer 4 is formed except for a stripe-shaped part. On the different layer 5, a coating layer having the same conductivity type as the clad layer 4 is formed to give a current constriction effect and a built-in waveguide effect. On the occasion, the coating layer is formed at least of three layers, and a second coating layer 25, second nearest to the active layer 3, is made to have a larger refractive index than the clad layer 4. A first coating layer 26 nearest to the active layer 3 and a third coating layer 28 third nearest are made to have a smaller refractive index than the coating layer 27. Thereby the effect of the shape of a stripe groove on the growth of a high refractive index layer is eliminated. This enables the attainment of a semiconductor laser having a refractive index waveguide structure wherein a horizontal mode is stable.