Ferroelectric fatigue and hysteresis of reactively sputtered Pb(Zr,Ti)O-3 (PZT) thin films were investigated by annealing IrO2 and Ir bottom electrodes at various temperatures. These electrodes were annealed to change their crystallinity and surface morphology in O-2 or N-2 atmosphere, respectively. There was no appreciable roughening of the PZT/IrO2 interface respective to that of the PZT/Ir; the rms roughness of IrO2 and Ir annealed at 650 degrees C was about 3.5 and 10 nm, respectively. The ferroelectric properties of the PZT/IrO2 were found to be overall better than those of the PZT/Ir. The PZT/IrO2 thin films exhibited very small fatigue up to 10(11) cycles; the P*r-P<^>r value decreased only from 16.6 to 14 mu C/cm(2) until 10(12) polarization reversals. This is due to the excellent diffusion barrier property of IrO2 and the smooth PZT/IrO2 interface. On the other hand, although thin IrO2 layer was formed between PZT and Ir, the PZT/Ir thin films began to undergo fatigue after 10(9) polarization reversals.