Abstract: A semiconductor laser formed into a double hetero junction structure comprising an n-type cladding layer and a p-type cladding layer with an active layer interposed therebetween. The p-type cladding layer has a laminated structure consisting of a first cladding layer of (Al.sub.x Ga.sub.1-x)InP disposed on one side adjacent to the active layer and a second cladding layer of Al.sub.y Ga.sub.1-y As disposed on the reverse side. A deterioration prevention layer of Al.sub.z Ga.sub.1-y As is included in the first cladding layer at a position spaced apart from the second cladding layer by a predetermined thickness. In addition, the second cladding layer is partially removed, and a current stricture layer is formed at the removed portion. Due to the above design, the semiconductor layer is capable of retaining high reliability with certainty.