A process of atomic layer deposition for the deposition of silicon oxide on a substrate, performed at room temperature, involving at least three precursors, being silicon tetrachloride, water and one Lewis base agent, being in various instances ammonia. The process comprises the steps of exposing on the substrate during an exposure time (a) the one Lewis base agent, (b) the silicon tetrachloride, and (c) the water. The process is remarkable in that at least one step of purge with nitrogen gas is performed after each of the steps (a), (b) and (c) during a purge time. Additionally, a film of silicon oxide which is remarkable in that it comprises a low level of chlorine contaminant and a significant degree of porosity with pores, the pores being in various instances micropores, mesopores or nanopores.