The formation of silicon dioxide layers by chemical oxidation of monosilane in a flow reactor at low temperature (100-250 degrees C) and by plasma chemical deposition in a planar reactor (20-180 degrees C) is investigated. The effect of temperature and pressure of the gas mixture (monosilane-dinitrogen oxide-helium) on porous structure and surface properties of the synthesized layers is investigated. Surface areas of the layers obtained in both types of reactors are measured using adsorption procedure. Adsorbates to serve as area standards were alcohols: methyl, ethyl, isopropyl, isobutyl, and toluene. It was established that within the range of area standards used (0.18-0.45 nm(2)), the surfaces of layers obtained both at 20 and 100 degrees C are fractal. The fractal dimension of their surface is determined. The character of changes in the surface structure of the layers obtained at different pressures is studied; this character indicates the decisive role of gas-phase stages in the mechanism of layer formation. This is confirmed by the data obtained for the plasma planar reactor in which the equilibrium is shifted to heterogeneous processes. (c) 2004 Elsevier B.V. All rights reserved.