The ongoing evolution from SiO 2 to insulator materials with lower dielectric constant, k, through the introduction of pores, brings new challenges in terms of processing and reliability. Porosity enhances penetration of undesired chemical species. A method of sealing microporous low-k dielectric chemical vapor deposited silicon oxycarbide films using UV-ozone induced oxidation has been investigated. The film thickness, refractive index, porosity, pore size, and sealing as a function of exposure time have been characterized by ellipsometry. The films are sealed without modification of the underlying porosity, an essential first step in integrating porous materials.