Spin-on glass (SOG) solutions for silicate and phosphosilicate films, respectively, were prepared by the sol-gel reaction of tetraethoxysilane (TEOS) in organic solvent. Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD) measurements were performed to investigate the bond configuration and thermal annealing behavior of the prepared films, respectively. The film properties, such as thickness shrinkage, refractive index and dielectric constant, were measured and correlated with the results of FTIR and TPD. The results of TPD combined with FTIR measurements inferred that the non-hydrolyzed alkoxy groups contained in silicate films were decomposed during the thermal treatment process, causing subsequent degradation of electrical properties of SOG films. Dielectric constants are well correlated with the content of silanol bonds in the films.