A semiconductor device including a substrate, lower electrodes disposed on the substrate, at least one support layer in contact with the lower electrodes, a dielectric layer disposed on the lower electrodes, an upper electrode disposed on the dielectric layer, a first interfacial film between the lower electrodes and the dielectric layer, and a second interfacial film between the upper electrode and the dielectric layer. At least one of the first and second interfacial films includes a plurality of layers, wherein the plurality of layers include a first metal element, and a second metal element, and at least one of oxygen \and nitrogen. The lower electrodes include the first metal element. A first region of the first interfacial film includes the second metal element at a first concentration and a second region of the first interfacial film includes the second metal element at a second concentration different from the first concentration.