Abstract: A semiconductor device includes conductive patterns, an insulating pattern between the conductive patterns, an insulating etch stop layer on the conductive patterns and the insulating pattern, a capacitor including first electrodes in contact with the first conductive patterns, a second capacitor electrode, and a dielectric between the first and second capacitor electrodes, an insulating structure covering the capacitor and the insulating etch stop layer, and a peripheral contact plug through the insulating structure and the insulating etch stop layer and including first through fifth plug regions stacked on top of each other, at least a portion of a side surface of the fourth plug region having an inclination angle different from inclinations angles of the third and fifth plug regions, and a vertical thickness of the fifth plug region being at least twice as great as a sum of vertical thicknesses of the first to fourth plug regions.