Transparent thin films with ultra water-repellency were prepared by a combined process of microwave plasma-enhanced CVD (MPECVD) and oxygen-plasma treatment. An organosilicon compound was used as a raw material for MPECVD. Mechanical properties, that is, hardness and wear resistance, of the ultra water-repellent thin films prepared by the combined process were improved in comparison with the films prepared by MPECVD without the oxygen-plasma treatment. The optical performance of the films remained unchanged.