Si0<sub>2</sub> films were fabricated on Si substrates by flame hydrolysis deposition (FHD) as buffer layer of waveguides. The
optical and surface properties of the films were characterized using scanning electron microanalyzer (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and variable angle spectroscopic ellipsometry (VASE). From a series of analyses, we demonstrated the excellent silica films fabricated. It proves that Si0<sub>2</sub> films prepared by flame hydrolysis deposition are entirely able to be applied in planar optical waveguides.
SiO2 thick films were deposited on silicon wafer (2 inches in diameter) as buffer layer for fabricating planar optical wave-guide by flame hydrolysis deposition (FHD) method. The deposition speed is as high as 8μ+m per minute. Then the deposited films were consolidated in electric furnaces in vacuum or air ambience at the temperature of 1380°C. As a result, transparent vitreous silica (or called silica glass) and semi-transparent cristobalite films were obtained. The thickness of the vitreous silica films is up to 40μm, and this kind of films is suitable for buffer layer of planar wave-guide. SiO2 thick films doped with GeO2 were obtained by the same process to fabricate the core layer. Finally, several factors affecting the consolidated silica films were discussed in detail.