A semiconductor laser according to the present invention comprises a λ/2 dielectric film (λ: in-medium wavelength of a dielectric film, for example, SiO2, Si3N4, Al2O3, and AlN) in contact with a facet of a resonator; and a first dielectric double layered film disposed on the dielectric film, which includes a first layer of a-Si and a second layer of a material having a refractive index lower than that of a-Si. The first layer has a thickness ¼ of an in-medium wavelength of a-Si, and the second layer has a thickness ¼ of an in-medium wavelength of the second layer. Therefore, it is possible to firmly stack the first dielectric double layered film and form a high reflectance film with high yield.