"Metal-oxide-semiconductor (MOS) capacitors with tandem aluminum oxides" (Al2O3) prepared by oxidation of aluminum in HNO3 with dc superimposed with ac anodization (DAC-ANO) compensation at room temperature was demonstrated. The technique of DAC-ANO was applied to repair the traps in the dielectrics. The electrical characteristics and reliability of various DAC-ANO compensated Al2O3/ANO-SiO2 stacked structures are discussed. The tandem Al2O3 MOS capacitor not only exhibits a reduced leakage current as compared to single Al2O3 MOS, but is also capable of resisting high voltage stress effectively. It was observed that the current variation percentage decreases with a strong voltage. The mechanism is given for this observation. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3211800] All rights reserved.