A stack-type image sensor include a first substrate comprising a photoelectric conversion element and a storage transistor connecting the photoelectric conversion element to a charge storage element; and a second substrate comprising a transfer transistor connecting the charge storage element to a floating diffusion, wherein the first substrate and the second substrate are stacked. The charge storage element comprises: a first electrode and a second electrode positioned adjacent to the first electrode and having a sidewall facing a sidewall of the first electrode, wherein the first electrodes and the second electrodes comprise at least one bonding pad formed in the first or second substrate; and a dielectric layer inserted between the sidewall of the first electrode and the sidewall of the second electrode, which face each other.