Provided are a unit pixel, an image sensor including the same, a portable electronic device including the same, and a method of manufacturing the same. The method of manufacturing includes: forming a photoelectric conversion region in a substrate; forming, in the substrate, a first floating diffusion region spaced apart from the photoelectric conversion region of the substrate, and a second floating diffusion region spaced apart from the first floating diffusion region; forming a first recess spaced apart from the first floating diffusion region and the second floating diffusion region by removing a portion of the substrate from a first surface of the substrate; filling the first recess to form a dual conversion gain (DCG) gate that extends perpendicularly or substantially perpendicularly from the first surface of the substrate; and forming a conductive layer to fill an inside of the first recess.