Very low cost room-temperature process to fabricate ultrathin Al2O3 high-k gate dielectrics with equivalent oxide thickness of 10 to 35 Angstrom was studied in this work. Anodic oxidation (anodization) in deionized water followed with rapid thermal annealing was used to oxidize ultrathin aluminum film. Unlike thermal oxidation, anodic Al2O3 possesses a speciality of self-limited oxide thickness. This work also demonstrated that the anodic Al2O3 exhibits gate dielectric quality characteristics, including low gate leakage current, low interface states, and low bulk trap density. The dielectric constant of anodic Al2O3 is estimated to be 9.7. In addition, the gate current density, Jg, is almost independent of the measurement temperature, revealing a low trap density and high thermal stability. These good insulator characteristics are believed to be related to the leakage path self-readjustment nature under electric field influence in liquid during anodization. (C) 2003 The Electrochemical Society.