JP2958204B

PURPOSE:To obtain a photodetector of high reliability which is excellent in transmittance in the light transmission band region, by setting the optical film thickness of each layer of a multilayered film so as to increase toward the outside arithmetical series-wise or geometrical series-wise. CONSTITUTION:A multilayered film 12 for shielding infrared radiation is formed on a light receiving substrate 11 for photoelectric conversion. The film 12 separates a plurality of lights different in wavelength in different optical paths, and intensively leads out only the light in a desired band region. The film 12 is constituted by laminating a plurality of dielectric films different in refractive index. When the center wavelength of a light which the multilayered film 12 is to transmit is lambda, the optical film thickness of a matched layer 13 is 0.7lambda/4, and the film is used as an antireflection film to the substrate 11. The optical film thickness of a low refractive index layer 14 is set to be 0.82lambda/8. The optical film thickness from a third layer to an eleventh layer is set to be an arithmetic series whose common difference is 0.03lambda/4. Hence the transmittance in the light transmission band region as a filter for cutting off infrared radiation is increased, and the light receiving sensitivity of a photodetector can be improved.