The barrier properties of the technologically attractive amorphous silica films depend on their structural characteristics at the atomic level, which, in turn are strongly influenced by the deposition conditions. In this paper, we propose an investigation of the poorly investigated densification mechanism of amorphous SiO2 films processed by CVD from TEOS and O2 between 400 and 550 °C. Based on literature survey and our original experimental results, we show that the densification process of these films, occurring with increasing the deposition temperature, is highlighted by a decrease of the water and silanol content, probed by transmission FTIR. We discuss the evolution of Si-O-Si related vibration signatures and we use the central force model to correlate the LO2 and LO3 shifts with the decrease of the Si-O-Si bond force constant, when the deposition temperature increases. Nuclear analysis reveals that films processed below 525 °C present hydrogen content between 5 ± 0.3 and 7 ± 0.3%at. Ellipsometry measurements attest that films processed at 550 °C are close to O/Si silica stoichiometry and hydrogen free. We show that application of the P-etch test results in particularly low erosion rate of 10 Å.s−1 for dense films processed at 550 °C.