Plasma-enhanced atomic layer deposition (PEALD) of iridium (Ir) films was investigated using Ir(EtCp)(COD) and NH3 plasma. Deposited Ir films had smooth surface and preferred (111) orientation. After simple annealing in ambient oxygen, surface roughening occurred because Ir was oxidized above 550 degrees C, and the oxidized IrO2 during temperature rising was reduced to Ir at 850 degrees C. However, by adopting two-step annealing, Ir films showed excellent thermal and morphological stability at 850 degrees C. During two-step annealing at 850 degrees C, the oxidation during temperature rising was suppressed by supplying argon, and annealing in ambient oxygen progressed after the temperature reached 850 degrees C. (C) 2008 The Electrochemical Society.