We fabricated TaN-gate electrodes on HfO(2) and SiO(2) films by wet etching using NH(4)OH/H(2)O(2) solution and investigated the electrical and structural properties of the TaN/SiO(2) and TaN/HfO(2) interfacial layers. The effective work function (phi(m.eff)) TaN on SiO(2) and HfO(2) are 4.4 and 4.6 eV, respectively. The phi(m.eff) on SiO(2) remained constant after post-metallization anneal (PMA) at temperatures of up to 750 degrees C and increased after 900 degrees C, but the phi(m.eff) on HfO(2) increased after PMA at 750 degrees C. The analysis by X-ray photoelectron spectroscopy (XPS) indicated that Ta oxide was formed near the TaN/SiO(2) and TaN/HFO(2) interfacial layers after the annealing at 900 degrees C. It was concluded that the instability is strongly associated with the Ta-O bond formation at the interfaces. (c) 2008 Elsevier B.V. All rights reserved.