An image sensor including a first semiconductor region of a first conductivity type that is arranged in a substrate, a second semiconductor region of a second conductivity type that is arranged in the first semiconductor region to form a charge accumulation region. The second semiconductor region includes a plurality of portions arranged in a direction along a surface of the substrate. A potential barrier is formed between the plurality of portions. The second semiconductor region is wholly depleted by expansion of a depletion region from the first semiconductor region to the second semiconductor region. A finally-depleted portion to be finally depleted, of the second semiconductor region, is depleted by the expansion of the depletion region from a portion of the first semiconductor region, located in a lateral direction of the finally-depleted portion.