A semiconductor device includes a plurality of lower electrodes having a vertical length greater than a horizontal width on a substrate, a supporter disposed between the lower electrodes, an upper electrode disposed on the lower electrodes, and a capacitor dielectric layer disposed between the lower electrodes and the upper electrode. The supporter includes a first element, a second element, and oxygen, an oxide of the second element has a higher band gap energy than an oxide of the first element, and the content of the second element in the supporter is from about 10 at % to 90 at %.