High-k hafnium oxide thin films were deposited on p-type (100) silicon substrate by laser molecular beam epitaxy (LMBE) technique, and these ultrathin gate dielectric films were characterized by Auger electron spectroscopy (AES), capacitance-voltage (C-V) and current-voltage (I-V) measurements. In order to take full advantages of high dielectric constant of HfO2, the growth of low dielectric constant interfacial layer must be controlled as thin as possible in the deposition process under optimized conditions. The effect of the critical factor of oxygen partial pressure was studied in the range of 2 x 10(-3) to 7 x 10(-6) Torr while keeping other experimental parameters constant. It was found that by lowering down the oxygen partial pressure to an optimized level, the growth of the low-k interfacial layer was effectively suppressed. A two-step deposition method was adopted to further reduce the thickness of this interfacial layer. The interfacial reaction was better controlled by using this two-step deposition method, resulting in high quality ultrathin HfO2 films on Si with desired and improved dielectric properties. (c) 2005 Elsevier B.V. All rights reserved.