A semiconductor laser device includes a substrate and an n-GaN layer composed
of
a nitride semiconductor formed on the substrate. The substrate includes a trench
having as a slope a plane inclined 62 degrees from the main plane of the substrate,
or a plane inclined within 3 degrees in an arbitrary direction from the inclined
plane. The n-GaN layer is formed on the slope. On the n-GaN layer are formed a
lower clad layer, an active layer, and an upper clad layer, each composed of a
nitride semiconductor. The active layer has a plane orientation substantially matching
the plane orientation of the main plane.
