Al2O3 gel films were prepared on poly(ethylene terephthalate) substrates from Al(O-sec-C4H9)(3) chemically modified with ethyl acetoacetate. A small roughness of about 20-50 nm was found to form on the Al2O3 gel films dried at room temperature and then immersed in hot water at 60 degrees C. When hydrolyzed fluoroalkyltrimethoxysilane was coated on the Al2O3 films, transparent thin films with contact angle for water to be more than 150 degrees were obtained.