Silica mesoporous films with low dielectric constant were successfully fabricated by a multiple step sol-gel process. The employment of inorganic/organic precursors proved very useful in preventing the film from cracking. The acid/base two-step catalysis could adjust the refractive index or porosity of the silica films effectively and easily. The basic properties of the silica films were evaluated by transmission electron microscopy, specular x-ray reflectivity, Fourier transform infrared spectroscopy, and thermal gravimetric, and differential thermal analysis. An inherently low dielectric constant of around 2.0 was realized for about 57% porosity in the silica film with a pore size less than 10 nm. The leakage current was at a level of 10(-6) A/cm(2) one month after fabrication. The dependencies of the dielectric properties of the films on the relative amount of the components in the starting solution and on the processing temperature were investigated in detail. Preliminary results of the silica films prepared here present a very positive prospective to an intermetal dielectric applications.