We investigated the effect of deposition temperature on the properties of the silicon oxide films produced by alternating exposures to bis(diethylamino)silane (BDEAS) and ozone (O3). The surface reactions during the deposition were studied using in situ characterization techniques and density functional theory (DFT) calculations. The atomic layer deposition (ALD) temperature window was between 250 and 350 °C with a nearly constant growth • rate of ∼ 0.10 nm/cycle and the step coverage higher than 94%. The saturation doses of BDEAS and O3/O2 were 5 × 106 L and 5 × 107 L. Among the films deposited in genuine ALD mode, the film deposited at 350 °C exhibited the lowest leakage current of 2.4 × 10-8 A/cm2 at −2 MV/cm and the lowest oxide trapped charge density of 6.5 × 1011/cm2. The in situ quartz crystal microbalance analysis showed that approximately 0.5 diethylamine ligand per BDEAS molecule was expected to remain on the surface after the BDEAS feeding. The in situ Fourier-transform infrared difference spectrum confirmed the presence of the ligand on the surface. DFT simulations showed that all NEt2 ligands are released on vicinal and geminal hydroxyl groups to form –SiH2*. However, only one NEt2 ligand can be removed on isolated hydroxyls because no other hydroxyls are nearby, resulting in –SiH2(NEt2)*.