PURPOSE: To suppress the spreading of an electric current in an optical waveguide layer so as to reduce the oscillation threshold of the layer by giving a semi-insulating property to the optical waveguide layer by adding an impurity which forms a deep level to the optical waveguide layer.

CONSTITUTION: A double hetero-structure composed of an active layer 12, optical waveguide layer 13, and semiconductor 14 of the second conductivity type having a wider inhibition band width than the active layer 12 has is formed on a semiconductor substrate 10 of the first conductivity type or on a semiconductor substrate of the first conductivity type on which a semiconductor layer 11 of the first conductivity type having a wider inhibition band width than the active layer 12 has is provided. A ridged waveguide structure having no semiconductor layer is formed on the optical waveguide layer 13 at parts of both side faces of a light propagating area 20 and in the area 20. Then a semi-insulating property is given to the layer 13 by adding an impurity which forms a deep level for catching numerous carriers of the second conductivity type to the layer 13. Therefore, this semiconductor laser having a low threshold current value can be obtained at a high yield, since no electric current is spread in the layer 13.