ZrO2/Al2O3 bilayer structure was investigated as one of potential replacements for SiO2 gate dielectric. Al2O3 and ZrO2 films were also examined and showed stoichiometric characteristics with negligible chlorine and carbon impurities. Al2O3 film exhibited an amorphous structure without interlayer formation while ZrO2 film showed a randomly oriented polycrystalline structure with amorphous phase of interlayer. ZrO2/Al2O3 bilayer film exhibited no interfacial layer between Si substrate and Al2O3 layers. The flat band voltage and hysteresis of ZrO2/Al2O3 bilayer film were 0.8 V and 150 mV, respectively, with fully reversible hysteresis. The measured leakage current of ZrO2/Al2O3 bilayer film was 1.2E-6 A/cm(2) with EOT value of 1.4 nm. ZrO2/Al2O3 bilayer film showed significantly enhanced gate oxide properties compared to those of the individual Al2O3 and ZrO2 films.