Provided are capacitors of semiconductor devices, wherein the capacitors may be used in a high-frequency operation environment. A capacitor includes a first electrode layer, a dielectric layer on the first electrode layer, and a second electrode layer on the dielectric layer, wherein the dielectric layer includes a plurality of unit dielectric layers, and the unit dielectric layer includes first and second sub-dielectric layers that have different dielectric constants and conductivities from each other and are connected in series, and the first and second sub-dielectric layers have a conductivity difference so that the capacitance of the dielectric layer converges to the capacitance of the unit dielectric layer.