Hard silicon dioxide MOO films were prepared by means of microwave plasma-enhanced CVD (MPECVD) using trimetylmethoxysilane (TMMOS) and CO2 as a row material and as an additive gas, respectively. The substrate temperature remained below 373 K. After preparation of the SiO2 films, the film surfaces were treated through a chemical method, that is, preparation of self-assembled monolayers of fluoroalkylsilane on the surfaces, in order to improve water repellency. This process was also conducted below 373 K. As a result of the chemical treatment, the water contacts angle of the films increased up to 150degrees. By this combined method, hard and ultra water-repellent silicon oxide films were successfully prepared. The films had high optical transparency. The high performance of the films was realized based on the mutual effect of surface hydrophobic groups and surface nanotextures. The films are expected to have wide applications in many engineering fields. (C) 2003 Elsevier Science B.V. All rights reserved.