A photo detector (200, 400) configured to absorb light in a unit pixel of an image sensor transforming the absorbed light to an electrical signal, comprising: a semiconductor substrate (210, 410) doped with first type impurities in which a groove is formed, the groove being V-shaped or U-shaped and having a predetermined angle; a light-absorbing part (250, 450) formed in a floated structure above the V-shaped or U-shaped groove, light being incident on the light-absorbing part (250, 450); an oxide film (240, 440) formed in between the light-absorbing part (250, 450) and the V-shaped or U-shaped groove, tunneling occurring in the oxide film (240, 440); a source (220, 420) formed adjacent to the oxide film (240, 440) on a slope of one side of the V-shaped or U-shaped groove and separated from the light-absorbing part (250, 450) by the oxide film (240, 440); a drain (230, 430) formed adjacent to the oxide film (240, 440) on a slope of the other side of the V-shaped or U-shaped groove and separated from the light-absorbing part (250, 450) by the oxide film (240, 440); and a channel interposed between the source (220, 420) and the drain (230, 430) and configured to form flow of an electric current between the source (220, 420) and the drain (230, 430), the channel being interposed along the groove when the groove is V-shaped and the channel being interposed in a lower area of the groove when the groove is U-shaped, wherein the light-absorbing part (250, 450) is formed of polysilicon doped with first type impurities, and the source (220, 420) and the drain (230, 430) are doped with second type impurities, first type impurities being p-type and second type impurities being n-type, wherein the light-absorbing part (250, 450) is insulated from the source (220, 420) and the drain (230, 430) by the oxide film (240, 440), wherein the photo detector is configured such that electron-hole pairs are generated in the light-absorbing part (250, 450) by the light incident on the light-absorbing part (250, 450), tunneling occurs in between at least one of the source (220, 420) and drain (230, 430) and the light-absorbing part (250, 450) by an electric field concentrated in the oxide film (240, 440), electrons of the generated electron-hole pairs are integrated in an area adjacent to the drain by applying an outside voltage to the drain (230, 430), and the electrons integrated in a boundary area of the light-absorbing part (250, 450) are moved to at least one of the source (220, 420) and the drain (230, 430) from the light-absorbing part (250, 450) by the tunneling, and the flow of the electric current of the channel is controlled by a change in the quantity of electric charge of the light-absorbing part caused by the moving of the electrons. a semiconductor substrate (210, 410) doped with first type impurities in which a groove is formed, the groove being V-shaped or U-shaped and having a predetermined angle; a light-absorbing part (250, 450) formed in a floated structure above the V-shaped or U-shaped groove, light being incident on the light-absorbing part (250, 450); an oxide film (240, 440) formed in between the light-absorbing part (250, 450) and the V-shaped or U-shaped groove, tunneling occurring in the oxide film (240, 440); a source (220, 420) formed adjacent to the oxide film (240, 440) on a slope of one side of the V-shaped or U-shaped groove and separated from the light-absorbing part (250, 450) by the oxide film (240, 440); a drain (230, 430) formed adjacent to the oxide film (240, 440) on a slope of the other side of the V-shaped or U-shaped groove and separated from the light-absorbing part (250, 450) by the oxide film (240, 440); and a channel interposed between the source (220, 420) and the drain (230, 430) and configured to form flow of an electric current between the source (220, 420) and the drain (230, 430), the channel being interposed along the groove when the groove is V-shaped and the channel being interposed in a lower area of the groove when the groove is U-shaped, wherein the light-absorbing part (250, 450) is formed of polysilicon doped with first type impurities, and the source (220, 420) and the drain (230, 430) are doped with second type impurities, first type impurities being p-type and second type impurities being n-type, wherein the light-absorbing part (250, 450) is insulated from the source (220, 420) and the drain (230, 430) by the oxide film (240, 440), wherein the photo detector is configured such that electron-hole pairs are generated in the light-absorbing part (250, 450) by the light incident on the light-absorbing part (250, 450), tunneling occurs in between at least one of the source (220, 420) and drain (230, 430) and the light-absorbing part (250, 450) by an electric field concentrated in the oxide film (240, 440), electrons of the generated electron-hole pairs are integrated in an area adjacent to the drain by applying an outside voltage to the drain (230, 430), and the electrons integrated in a boundary area of the light-absorbing part (250, 450) are moved to at least one of the source (220, 420) and the drain (230, 430) from the light-absorbing part (250, 450) by the tunneling, and the flow of the electric current of the channel is controlled by a change in the quantity of electric charge of the light-absorbing part caused by the moving of the electrons.