An embodiment of the FeRAM includes a ferroelectric capacitor including a bottom electrode, a ferroelectric layer, and a top electrode. Strontium ruthenium oxide is formed between the bottom electrode and the ferroelectric layer and between the ferroelectric layer and the top electrode. A diffusion barrier layer including strontium ruthenium oxide and iridium is formed between the top electrode and a direct cell contact plug coupled to a plate line interconnecting top electrodes of ferroelectric capacitors. Thus, diffusion of nitrogen or metallic materials produced in subsequent processes is suppressed to prevent degradation of the ferroelectric layer.