A semiconductor laser device having an active region including alternating layers
of at least one quantum well layer and a plurality of barrier layers, where two
of the plurality of barrier layers are the outermost layers of the alternating
layers. Each of the at least one quantum well layer has a compressive strain, and
each of the plurality of barrier layers has a tensile strain. In the active region,
a strain buffer layer having an intermediate strain is formed between each quantum
well layer and each of two barrier layers adjacent to the quantum well layer. Interfacial
strain is thus reduced, improving high-output-power characteristics.