Abstract: A semiconductor laser comprises a semiconductor substrate provided in its major surface with a strip mesa, and a laminated structure constructed by sequentially forming, through the epitaxial deposition of semiconductor materials on the major surface of the semiconductor substrate, at least a first semiconductor layer serving as a first conduction type cladding layer, a second semiconductor layer serving as an active layer, a third semiconductor layer serving as a second conduction type cladding layer, and a fourth semiconductor layer serving as a light absorbing or current blocking layer by utilizing the crystallographic principle and the characteristics of the steps formed by the strip mesa so that faults are formed in the laminated structure so as to extend along the direction of extension of the opposite longitudinal side surfaces of the strip mesa.