PURPOSE: To preserve a diffraction grating excellently, and to improve yield on manufacture by forming a semiconductor layer in low impurity-carrier concentration onto the diffraction grating and previously laminating a semiconductor layer in high concentration onto the semiconductor layer in a semiconductor laser having laminated structure containing an active layer, a guide layer and the diffraction grating.

CONSTITUTION: An active layer 2, a guide layer 3 and a diffraction grating 4 are shaped onto an N type InP substrate 1, and a P type InP clad layer 6 and a P type InP clad layer 7 are laminated continuously onto the diffraction grating 4. In the constitution, impurity carrier concentration in the clad layer 6 is brought to approximately 1×1017/cm3, and thickness thereof is brought to approximately 0.1μm on measuring from the throughs of the grating 4. Impurity carrier concentration in the clad layer 7 is brought to approximately 1×1018/cm3 and thickness thereof to approximately 1μm. Accordingly, the grating ca be preserved with excellent reproducibility in depth of approximately 500∼600 even after the grating 4 is formed, and oscillating threshold currents at room temperature and a laser having high differential quantum efficiency is obtained.