A semiconductor laser device has an active layer, a first cladding layer
formed on the active layer, and a second cladding layer formed on the
first cladding layer. The first cladding layer is doped with magnesium as
a first impurity to have a high resistivity. The second cladding layer is
doped with zinc as a second impurity to have a resistivity lower than the
resistivity of the first cladding layer.