Patent ID: 8587709

Claim:
A high-speed charge-transfer photodiode connected to a charge-collection region having a constant depletion potential, comprising: a first conductivity type semiconductor layer serving as a charge-generation region; and a second conductivity type surface-buried region being continuous to the first conductivity type semiconductor layer as a same semiconductor layer, selectively buried in a part of an upper portion of the semiconductor layer, serving as a charge-transfer region of charges generated by the charge-generation region, wherein a specified direction directed toward the charge-collection region, in the surface-buried region provided along a plane parallel to a surface of the semiconductor layer, is assigned as a charge-transfer direction of the charges, and at least one of a variation of widths of the surface-buried region defined in an orthogonal direction to the charge-transfer direction and a variation of impurity concentration distributions of the surface-buried region, which are measured along the charge-transfer direction, is determined such that an electric field distribution in the charge-transfer direction is constant in the entire region of the charge-transfer region.