PURPOSE: To facilitate control of the thickness of an epitaxial growth layer in each of the grooves, by providing an active layer which is sandwiched between clad layers of first and second conductivity types and has a curvature toward the substrate in the center of each of the stripe-shaped grooves.

CONSTITUTION: The surface of a substrate of a first conductivity type having a crystal plane which is ±1°∼±3° inclined from the [100] axis toward the [011] axis and -0.2°∼+0.2° inclined from the [100] axis toward the [011] axis is etched to form stripe-shaped grooves extending parallel to the axis thereof. A clad layer of a first conductivity type, an active layer which is undoped or has either the first or second conductivity type, a clad layer of the second conductivity type, and a cap layer of the first conductivity type are grown on the substrate. The growth rate of the layer on the stripe-shaped grooves is much lower than that of the layer on the stripe-shaped grooves parallel to the [011] axis conventionally formed in the (100) plane by etching. Therefore, even when a growth solution is sufficiently supersaturated so that the shoulders of each groove are not melted back, it is easy to effect control of the thicknesses of the clad layer of the first conductivity type and the active layer.