ZrO2 dielectric layers were grown on p-type Si(100) by metalorganic molecular beam epitaxy. Zirconium t-butoxide, Zr(O∙t-C4H9)4 was used as a Zr precursor for its moderate vapor pressure. The properties of the layers were evaluated by x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, x-ray diffraction, and capacitance–voltage (C–V) and current–voltage (I–V) analyses. At a low O2/Ar flow ratio, a fully oxidized ZrO2 layer was not obtained and metallic zirconium was incorporated in the layer. A higher oxygen-flow rate was required to diminish the interfacial charge effects. As the oxygen-flow rate increased, the faster change from the accumulation to the inversion state at depletion region and flatband (FB) voltage shift (ΔVFB∼0.2 V) appeared. The observed microstructure indicates that the grown layer was polycrystalline, which was the main reason for the degradation of the electrical properties. From the I–V analysis, a current density of -7.0×10-3 A/cm2 was measured at -1.5 V gate voltage. A dielectric constant of 18–19 was calculated from the C–V measurements. © 2003 American Vacuum Society.