A ferroelectric capacitor and a method of manufacturing the same are provided, wherein the ferroelectric capacitor of a semiconductor device, which sequentially includes a lower electrode, a ferroelectric layer, and an upper electrode on a conductive layer connected to a transistor formed on a semiconductor substrate, includes an oxidation preventing layer between the conductive layer and the lower electrode. The oxidation preventing layer prevents the conductive layer from being oxidized during high-temperature heat treatment of the ferroelectric layer. Accordingly, the oxidation resistivity of the interfaces of the conductive layer, used as a storage node, and the lower electrode, which faces the conductive layer, increases, so a temperature at which a ferroelectric thin layer is formed can be also increased. Consequently, a ferroelectric thin layer having excellent characteristics may be obtained.