The present work deals with the formation of "hybrid" waveguides by using SiO2 as a core material deposited by Low Pressure Chemical Vapor Deposition onto fully oxidized porous silicon cladding layers. The idea is related to the observation in all-pc,rous silicon guides of a progressive reduction of the interface quality between core and cladding with depth. The porous silicon oxidation process is found to reduce the refractive index down to 1.15 for starting material with 0.8 porosity. The refractive index contrast of the guide is estimated to be approximate to0.2. Strips have been defined by photolithography, with good guiding performances. Optical lithography, as well as other technological processes can be performed onto the SiO2 layer without damaging the underlying porous structure.