Au-catalyzed growth of nanocrystalline Si by pulse jet chemical vapor deposition hasbeen investigated. Au thin film was first deposited on thermally oxidized Si(100), then CH3SiH3pulse jets were irradiated onto the Au/SiO2/Si(100) surface. The irradiation of the CH3SiH3 jets at1150 °C resulted in circular patterns with a diameter of ~40 μm on the sample surfaces. In thecenter of the circular patterns, agglomerations of Au were observed. It was found that the oxidelayer was etched and that nanocrystalline Si with diameters ~500 nm was formed in the circularpatterns. These results indicate that the nanocrystalline Si was grown by the VLS process in whichSi atoms were supplied from the oxide layer, Si substrate, and CH3SiH3 molecules.