We report on a high-k lanthanum oxide (La2O3) gate dielectric deposited on Si substrate by reactive radio-frequency sputtering for Al and Al/TaN metal gate electrode. The La2O3 gate dielectric film with Al/TaN gate electrode exhibited excellent electrical properties such as low equivalent oxide thickness, high electric field breakdown, excellent reliability, and almost no hysteresis in C-V curves comparable to that with Al gate electrode. This indicates that Al/TaN metal gate can inhibit Si atoms outdiffusion from Si substrate and the diffusion of Al atoms in the oxide from secondary ion mass spectrometry data. Moreover, post-processing treatments can passivate a large amount of trapped charge at defect sites. (c) 2007 The Electrochemical Society.