A capacitor may include a lower electrode, a dielectric layer structure on the lower electrode, and an upper electrode on the dielectric layer structure. The dielectric layer structure may include a plurality of dielectric layers and at least one insert layer structure between ones of the plurality of dielectric layers. The insert layer structure may include a plurality of zirconium oxide layers and at least one insert layer. The insert layer may be between ones of the plurality of zirconium oxide layers. The capacitor may have a high capacitance and low leakage currents.