Mixed oxide TiO2/SiO2 dielectrics have been deposited at room temperature by microwave excited plasma enhanced chemical vapor deposition from SiH4 and TiCl4 precursor gases. The low frequency dielectric constant and the refractive index at 632.8 nm are observed to increase linearly with increasing Ti concentration. No anomalous enhancement of the dielectric constant at low Ti concentrations is observed, consistent with the conclusion that the Ti ion replaces the Si ion directly in fourfold coordination. A compound dielectric constant of 25 can be achieved for a concentration similar to 50% Ti where it is anticipated the optical band gap would be similar to 6.25 eV. (c) 2006 American Vacuum Society.