The infrared absorption of thermal SiO2has been measured using the attenuated total reflectance technique. The samples were subjected to various water diffusion and annealing treatments. Electron trapping was also measured in similar samples. The infrared measurements show the presence of SiH, SiOH, and H2O groups in the SiO2films, particularly after H2O diffusion. Examination of both the infrared absorption results and the electron trapping results show that the electron trap with a cross section of 1×10−17cm2is associated with SiOH groups, and that the electron trap with a cross section of 2×10−18cm2is associated with H2O.