Innovation of growth-then-anodization technique is introduced in this work to prepare high-quality ultrathin gate oxides. In repeated direct-current anodization (RDC-ANO) process, the first oxides were prepared by DC5V-ANO with thin and thick thickness followed by rapid thermal anneal. The repeated anodizations were carried out by various dc voltages and also followed by the same anneal. It was found that when the voltage of the repeated ANO is higher than that of the first ANO, the RDC-ANO oxides will superior to the one time grown DC-ANO ones provided that the first oxide thickness is thin enough. The electrical improvements include reduced leakage, higher time-zero dielectric breakdown (TZDB), and time-dependent dielectric breakdown (TDDB) endurance. In rapid thermal oxide followed by anodization process, the anodization technique of direct current superimposed with alternating-current anodization (DAC-ANO) is applied to repair the traps of thermally grown ultrathin gate oxides. Effects of anodization time and thermal oxide thickness are inspected. It was experimentally observed that the quality of thermal oxides is well improved by this proposed growth-then-anodization method. The electrical improvements include reduced leakage, better uniformity and less stress-induce-leakage-current (SILC) behavior. (C) 2004 The Electrochemical Society.