A backside illuminated image sensor includes a photodiode, formed below the top surface of a semiconductor substrate, for receiving light illuminated from the backside of the semiconductor substrate to generate photoelectric charges, a reflecting gate, formed on the photodiode over the front upper surface of the semiconductor substrate, for reflecting light illuminated from the backside of the substrate and receiving a bias to control a depletion region of the photodiode, and a transfer gate for transferring photoelectric charges from the photodiode to a sensing node of a pixel.