Planarization of dielectric materials in multilevel devices has become an important topic in recent years. Planarization achieved through chemical/mechanical polishing (CMP) is the foremost of the techniques available to provide an appropriate low-topography surface for accurate lithography. In this study the effects of the planarization process on deposited SiO2 films, a material to which CMP is frequently applied, have been examined. The analysis, completed using transmission electron microscopy and Fourier-transform infrared spectroscopy, revealed evidence of chemical/structural modification of the SiO2 to 100-200 nm from the polished surface and more heavily altered or deformed regions extending to a few tens of nm in depth.