A backside illuminated image sensor includes a light receiving element disposed in a first substrate, an interlayer insulation layer disposed on the first substrate having the light receiving element, an align key spaced apart from the light receiving element and passing through the interlayer insulation layer and the first substrate, a plurality of interconnection layers disposed on the interlayer insulation layer in a multi-layered structure, wherein the backside of the lowermost interconnection layer is connected to the align key, a passivation layer covering the interconnection layers, a pad locally disposed on the backside of the first substrate and connected to the backside of the align key, a light anti-scattering layer disposed on the backside of the substrate having the pad, and a color filter and a microlens disposed on the light anti-scattering layer to face the light receiving element.