Amorphous zirconia thin films were deposited directly on silicon-on-insulator (SOI) substrates with thin top silicon by ultra-high vacuum electron beam evaporation. Spreading resistance profile and scanning transmission-electron microscopy (TEM) were used to detect the interface quality and microstructure, revealing that the interface between the zirconium oxide films and top silicon was abrupt and clear. The films kept to be amorphous up to the rapid thermal temperature of 700°C for 300s, but arriving at 700°C an unknown interfacial product appeared,which was probably ZrSixOy. High frequency capacitance-voltage (C- V) characteristics at 1 MHz performed on metal-oxide-SOI structure revealed that this interfacial product exhibited good electrical properties of zirconia thin films. When the annealing temperature increased from 600°C to 700°C, flat voltage VFB changed from -2.451 to -1.741 eV, showing the improvement in the quality of the films. The cumulative region capacitance decreased from 3.058 × 10-11F to 3.012 × 10-11F, indicating increasing equivalent oxide thickness, which is in agreement with the result of high-resolution cross-sectional TEM.