An image sensor includes a substrate having a first surface and a second surface opposite to each other, a first floating diffusion region provided in the substrate and being adjacent to the first surface, a through-electrode provided in the substrate and electrically connected to the first floating diffusion region, an insulating structure, a bottom electrode, a photoelectric conversion layer, and a top electrode sequentially stacked on the second surface, a color filter buried in the insulating structure, and a top contact plug penetrating the insulating structure to connect the bottom electrode to the through-electrode.