HfO2 dielectric layers were grown directly on the p-type Si (1 0 0) by metalorganic molecular beam epitaxy, (MOMBE). Hafnium tetra-butoxide was used as a Hf precursor and pure oxygen was introduced to form an oxide layer. The properties of the layers with different thicknesses were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). high-resolution transmission electron microscopy (HRTEM), and capacitance-voltage (C-V) and current-voltage (I-V) analyses. XRD and HRTEM results showed that the HfO2 films thinner than 12 nm were amorphous while the films thicker than 12 am began to crystallize in the tetragonal and the monoclinic phases. The XPS spectra of O 1s -show that the O-Si binding shifted to the lower binding energy with increasing the HfO2 layer thickness. Moreover. the snap back phenomenon is observed in accumulation capacitance. These changes are believed to be linked with the decomposition of SiO and the crysiallization of HfO2 layer during the film growth. (C) 2004 Elsevier B.V. All rights reserved.