Two step-derived SiO2 sol was deposited on Si(100) substrate via spin coating. After aging and washing of wet gel film, surface modification with TMCS (trimethylchlorosilane) was followed to prevent additional condensation reaction during drying. Dried films were heated at different temperatures. The effects of heating temperature on the chemical bonding state of SiO2 thin film were investigated by means of FTIR and XPS analyses. After heating at different temperatures (200-500 degrees C), crack-free SiO2 thin films were synthesized with thickness of 300-500 nm, refractive indices of 1.23-1.15 and dielectric constant of 2.2-2.8. Also the film heated at 300 degrees C exhibited leakage current density below 10(-5) A/cm(2) under an electrical field of 2 MV/cm.