1. An image sensor comprising: a semiconductor substrate having a first conductivity type; a deep well having a second conductivity type, the deep well being formed at a predetermined depth in the semiconductor substrate to divide the semiconductor substrate into a first conductivity type upper substrate area and a lower substrate area; and a plurality of unit pixels integrating charges corresponding to incident light and comprising first conductivity type ion-implantation areas said first conductivity type ion-implantation areas are separated from one another, at least one unit pixel among the plurality of unit pixels further comprising the first conductivity type upper substrate area that is positioned under a first conductivity type ion-implantation area included in the unit pixel, extends beyond the first conductivity type ion-implantation area and is electrically isolated from first conductivity type ion-implantation areas included in adjacent unit pixels of said plurality of unit pixels, wherein the first conductivity type ion-implantation areas are defined by a second conductivity type first isolation well and wherein the first isolation well extends to at least substantially the same depth as or deeper than the ion implantation areas, wherein the first conductivity type upper substrate area included in the at least one unit pixel is wider than the first conductivity type upper substrate area included in each of the unit pixels other than the at least one unit pixel among the plurality of unit pixels.