An image sensor and a method for fabricating the same are provided to reduce conjuncture capacitance of a floating diffusion region by dividing the floating diffusion region into two parts. A gate electrode(210) of a transmission transistor is formed a first conductive semiconductor substrate. A photodiode is formed on one end of the gate electrode in the substrate. An interlayer dielectric is formed on the substrate. A contact(430) penetrates the interlayer dielectric to be connected to the substrate. A second conductive floating diffusion region is formed in a region corresponding to the other end of the gate electrode in the substrate. A high-concentration ion implantation region(520) is formed in the area in which the contact contacts the substrate, and a low-concentration ion implantation region(510) is formed in the remaining area.
