The use of flame hydrolysis deposition (FHD) to fabricate porous silica glass soot in the B2O3-P2O5-SiO2 glass system (BPSG) is described for silica-on-silicon device applications. The deposition conditions with a Si substrate temperature (similar to 200 degrees C) and a flame temperature (1300-1500 degrees C) are appropriate to synthesize the SiO2 and P2O5-SiO2 non-crystalline glass soot. However, further investigations for the B2O3-P2O5-SiO2 glass soot are needed to obtain complete amorphous phases. The densification process of porous silica glass soot in the three systems of SiO2, P2O5-SiO2 and B2O3-P2O5-SiO2 is also described to estimate the onset of sintering temperature. The OH absorption measurements are performed to try to identify incorporation of hydroxyl contaminants in the systems of P2O5-SiO2 and B2O3-P2O5-SiO2.