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 O-2/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 (DeltaV(FB) similar to0.2 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 X 10(-3) A/cm(2) was measured at -1.5 V gate voltage. A dielectric constant of 18-19 was calculated from the C-V measurements. (C) 2003 American Vacuum Society.