The present disclosure relates to a memory device, and more particularly, to a memory device including a substrate, a plurality of vertical structures disposed on the substrate and including insulation layers and lower electrodes, which are alternately laminated with each other, wherein the vertical structures are aligned in a first direction parallel to a top surface of the substrate and a second direction crossing the first direction, an upper electrode disposed on a top surface and side surfaces of each of the vertical structures, and a first dielectric layer disposed between the upper electrode and the vertical structures to cover the top surface and the side surfaces of each of the vertical structures. Here, the first dielectric layer includes a ferroelectric material.