A pixel of an image sensor includes a photoelectric conversion region formed in a semiconductor substrate, a floating diffusion region formed in the semiconductor substrate, the floating diffusion region being spaced apart from the photoelectric conversion region, a vertical transfer gate extending from a first surface of the semiconductor substrate into a recess in the semiconductor substrate, and configured to form a transfer channel between the photoelectric conversion region and the floating diffusion region, and an impurity region surrounding the recess. The impurity region has a first impurity concentration at a region adjacent to a side of the recess, and a second impurity concentration higher than the first impurity concentration at a region adjacent to the bottom of the recess.