A semiconductor laser comprising an active waveguide formed of a compound semiconductor comprising a Group V element phosphorous, comprised of an active layer and two cladding layers that hold the active layer between them, and a current confinement structure formed on the active waveguide by the use of a compound semiconductor comprising Group V element arsenic. This semiconductor laser can achieve a small astigmatism, a low threshold current and a low operation current. Also disclosed is a method of fabricating a semiconductor laser having characteristic features that the crystal growth may be carried out only twice, the movement of the impurities in crystals does not easily occur, a regrowth interface with a very little defect can be readily obtained, and the structure wherein the outer cladding layer has a smaller width at its portion nearer to the active waveguide can be naturally formed.