Method of making a semiconductor laser device

A method of making a distributed feedback semiconductor laser device comprising the steps of:

• growing, on an InP substrate of a first conductivity type, a first InP current blocking layer of a second conductivity type opposite said first conductivity type;
• forming a groove in said first InP current blocking layer extending in depth to said InP substrate and having a predetermined width;
• growing is said groove an InP buried layer of said first conductivity type having a thickness substantially equal to that of said first InP current blocking layer;
• forming a ridge including a double heterojunction structure comprising a first InP cladding layer of said first conductivity type, an InGaAsP active layer, and a second InP cladding layer of said second conductivity type including a diffraction grating layer of InGaAsP therein, said first InP cladding layer, said active layer, and said second cladding layer being substantially planar and stacked in the named order on said InP buried layer and having a width of the same order as that of said InP buried layer;
• growing a second InP current blocking layer of said first conductivity type on said first InP current blocking layer of said second conductivity type to bury said ridge in said second InP current blocking;
• and
• growing a contact layer of said second conductivity type disposed opposite and in contact with said second InP current blocking layer and said second InP cladding layer.