A semiconductor laser device is one of AlGaInAs semiconductor laser
devices, and has a multi-layer structure with a n-GaAs substrate on which
a n-Al.sub.0.3Ga.sub.0.7As buffer layer, a n-Al.sub.0.47Ga.sub.0.53As
clad layer, active layer portion, p-Al.sub.0.47Ga.sub.0.53As clad layer
and p-GaAs cap layer are formed. The active layer portion is configured
as a multi-layer structure including
(Al.sub.0.37Ga.sub.0.63).sub.0.97In.sub.0.03As light guide layer,
Al.sub.0.1Ga.sub.0.9As active layer and
(Al.sub.0.37Ga.sub.0.63).sub.0.97In.sub.0.03As light guide layer. By
using the AlGaInAs layer to which In is added is used as the light guide
layers, the active layer is under compressive strain. Accordingly, the
lattice constant of the active layer at the laser emitting edge becomes
smaller due to a force from the adjacent light guide layers. The band gap
energy of the active layer near the laser emitting edge becomes larger
than the inside of laser device, thereby forming the window structure.