To reduce a dark current of an image sensor including a photoelectric conversion unit disposed on a back surface of a semiconductor substrate.
The image sensor includes a photoelectric conversion unit, a through-electrode, a charge holding unit, a back-side high impurity concentration region, and a front-side high impurity concentration region. The photoelectric conversion unit is disposed on a back surface of a semiconductor substrate and performs photoelectric conversion of incident light. The through-electrode is formed in a shape penetrating from the back surface to a front surface of the semiconductor substrate and transmits a charge generated by the photoelectric conversion. The charge holding unit is disposed on the front surface of the semiconductor substrate and holds the transmitted charge. The back-side high impurity concentration region is disposed in a region adjacent to the through-electrode on the back surface of the semiconductor substrate and is formed to have a higher impurity concentration than an impurity concentration of a region adjacent to the through-electrode at the central portion of the semiconductor substrate. The front-side high impurity concentration region is disposed in a region adjacent to the through-electrode on the front surface of the semiconductor substrate and is formed to have a higher impurity concentration than the impurity concentration of the region adjacent to the through-electrode at the central portion of the semiconductor substrate.