PURPOSE: To provide a photoelectric conversion device that delivers a high multiplication factor and is excellent in response speed even at the application of low voltage, and that can be formed on a semiconductor substrate having a circuit formed thereon by reducing defective levels in the boundary of step back heterojunctions in a multiplication layer, eliminating spikes and notches in the heterojunctions, thereby improving the mobility of carriers and suppressing the recombination of carriers.

CONSTITUTION: This photoelectric conversion device is one wherein a light absorption layer 104 and a carrier multiplication layer 103 are composed of non-single crystal materials, and the carrier multiplication layer 103 is composed of a plurality of layers 111, 112 and 113 having continuously graded forbidden band width. Distortion relaxation layers 114, 115 and 116 are formed in the areas between the above-mentioned layers where forbidden band width is discontinuously varied; the distortion relaxation layers 114, 115 and 116 are obtained by alternately forming ultrathin film layers 114-1, 114-2 and 114-1',... composed of single crystal materials having two or more different compositions.