[en] Intensive research has been carried out in recent years into nonthermal activation of the processes of surface treatment of semiconductor materials with the formation of film structures. In addition to laser radiation whose physics of interaction with the solid has been studied most extensively, these investigations have been carried out using other physical methods of activation - electric field, and ultraviolet radiation, which have been studied less extensively. All of these methods are characterised by the localisation of the energy effect in sub-surface the regions of the solid and, consequently, by the absence of secondary processes of migration and degradation in its volume. This is a considerable advantage of the processes in this direction in comparison with conventional processes, with their total thermal effect of the entire crystal. One of these processes is the production of thin films of silica on neutral and active substrates by gas-phase deposition from a mixture of tetraetoxysilane (TEOS) on the surface of a silicon substrate during the process of formation of silica film under the effect of ultraviolet radiation. The theoretical basis of the evaluation was a presented by the following considerations. The energy effect of ultraviolet radiation on the TEOS molecule takes place twice: directly in the gas phase as a result of absorption of the radiation energy by the molecules (and their excitation) and later: the surface of silicon as a result of the absorption of radiation energy by surface active centres and the transfer of the adsorbed excitation energy to the molecules adsorbed on them. Since the mean activation energy of dissociation of the TEOS molecule in the non-excited state is quite high (∼ 3500 kJ/mole), we did not consider the low-probability breakdown of the molecules in the gas phase and consider dissociation only with the surface of the substrate taking part in it