A unit pixel of an image sensor includes a photoelectric conversion region, an isolation region, a floating diffusion region and a transfer gate. The photoelectric conversion region is formed in a semiconductor substrate. The isolation region surrounds the photoelectric conversion region, extends substantially vertically with respect to a first surface of the semiconductor substrate, and crosses the incident side of the photoelectric conversion region so as to block leakage light and diffusion carriers. The floating diffusion region is disposed in the semiconductor substrate above the photoelectric conversion region. The transfer gate is disposed adjacent to the photoelectric conversion region and the floating diffusion region, extends substantially vertically with respect to the first surface of the semiconductor substrate, and transmits the photo-charges from the photoelectric conversion region to the floating diffusion region.