A semiconductor device and a method of manufacturing a semiconductor device, the device including a substrate; a lower structure including pad patterns on the substrate, upper surfaces of the pad patterns being at an outer side of the lower structure; a plurality of lower electrodes contacting the upper surfaces of the pad patterns; a dielectric layer and an upper electrode sequentially stacked on a surface of each of the lower electrodes; and a hydrogen supply layer including hydrogen, the hydrogen supply layer being between the lower electrodes and closer to the substrate than the dielectric layer is to the substrate.