We report the characterization of aluminum oxide (Al2O 3) films which are grown on Si substrates by electron beam evaporator. This paper focuses on the characteristic variation of Al2O3 films depending on the different annealing techniques, such as post-deposition annealing and post-metallization annealing. The capacitance-voltage (C-V) curves indicate a negative charge and interface trap charge density between the Al2O3 film and Si interface. The current-voltage (I-V) curves show a leakage current. The x-ray diffraction (XRD) patterns show the crystallinity of Al2O3 films. Based on the results, the annealing effect is important condition to increase negative fixed charge in the Al2O3 films.