Thin Al2O3 films were prepared using a special evaporation cell permitting to grow clean and stoichiometric layers in ultrahigh vacuum conditions. The layers were deposited on silicon substrates at different preparation conditions. The obtained films were characterized by Auger electron spectroscopy (AES, in situ) and by XPS (ex situ) methods. The good quality of layers, shown by the electron spectroscopy methods, was confirmed by capacitance-voltage (C-V) electrical measurements.