HfO 2 dielectric layers were grown on the p-type Si(1 0 0) substrate by metal-organic molecular beam epitaxy (MOMBE). Hafnium-tetrabutoxide [Hf(Oβ’t-C 4 H 9 ) 4 ] was used as a Hf precursor and argon gas was used as a carrier gas. The microstructure and thickness of HfO 2 films were measured by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The electrical characteristics of the HfO 2 layers were evaluated by high frequency (HF) capacitance-voltage (C-V) and current-voltage (I-V) measurements. The surface morphology, crystal structure, and chemical binding states of HfO 2 films were also examined by atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) measurements. HF C-V and I-V measurements have shown that HfO 2 layer grown by MOMBE has higher dielectric constant (k) of 20-22 and lower leakage current density of βΌ10 -8 A/cm 2 compared with the conventional SiO 2 . In addition, it has been shown that the HfO 2 layer has fixed oxide charge of about 8 Γ 10 11 cm -2 and interfacial state density of about 1 Γ 10 12 eV -1 cm -2 . The electrical characteristics and surface morphology of HfO 2 films are affected by O 2 /Ar gas flow ratio. Finally, post-metallization annealing (PMA) was carried out to reduce the interface state density.