ZnO thin films were deposited on silicon substrate by RF magnetron sputtering using metallic zinc target. A systematic study has been made of the influence of oxygen concentration and the RF power on the. films structural properties. They exhibited a c-axis orientation of below 0.32degrees FWHM of X-ray rocking curves, an extremely high resistivity of 10(12) Omega cm and an energy gap of 3.3 eV at room temperature. It was found that a RIF power of 50 W, target to substrate distance 70 mm, very low gas pressures of 3.35 x 10(-3) Torr in argon and oxygen mixed gas atmosphere giving to ZnO thin films a good homogeneity and a high crystallinity. (C) 2003 Elsevier Science B.V. All rights reserved.