An image sensor includes a photoelectric conversion element and a charge storage node coupled to the photoelectric conversion element. The charge storage node may store photocharges generated in the photoelectric conversion element. The charge storage node may include a floating diffusion region in a semiconductor substrate, a barrier dopant region on the floating diffusion region in the semiconductor substrate, and a charge drain region on the barrier dopant region in the semiconductor substrate, where the semiconductor substrate is associated with a first conductivity type, the floating diffusion region is associated with a second conductivity type, the barrier dopant region is associated with the first conductivity type, and the charge drain region is associated with the second conductivity type.