A method of fabricating a ridge-waveguide type semiconductor laser device having
a large half-value width and a high kink level is provided. First, an effective
refractive index difference n between an effective refractive index neff1
of the ridge and an effective refractive index neff2 of a portion on
each of both sides of the ridge is taken as n=neff1-neff2,
and a ridge width is taken as W. On such an assumption, constants "a", "b", "c",
and "d" of the following three equations are set on X-Y coordinates (X-axis: W,
Y-axis: n) The first equation is expressed by naW+b,
where "a" and "b" are constants determining a kink level. The second equation is
expressed by Wc, where "c" is a constant specifying a minimum ridge width
at the time of formation of the ridge. The third equation is expressed by nd,
where "d" is a constant specified by a desired half-width value para.
Then at least either of a kind and a thickness of an insulating film, a thickness
of an electrode film on the insulating film, and a kind and a thickness of a portion,
located on each of both the sides of the ridge, of the upper cladding layer is
set in such a manner that a combination of n and W satisfies the above three equations.
