To provide an X-ray CCD with which detection sensitivity of X rays can be improved.

An epitaxial semiconductor layer 2 is formed on an N-type semiconductor substrate 1, and a charge transfer channel 3 is formed in the epitaxial semiconductor layer 2, so that the increase in the impurity concentration in the semiconductor layer 2 due to the diffusion of impurities from the substrate 1 can be prevented. Consequently, the thickness of a depletion layer formed in the semiconductor layer 2 can be increased. The dark current, which tends to increase due to the thicker depletion layer, is absorbed in the substrate 1 side by applying a reverse bias between the substrate 1 and the semiconductor layer 2.