The two-dimensional modelling of the etching of silicon oxide in CF4 + H, plasma is considered. The profiles of etched trenches at real dimensions are calculated as a function of mask dimensions, concentrations of chemically active and non-active plasma components and ion bombardment parameters. The chemical composition of CF4 + H-2 plasma is calculated, the plasmochemical etching (PCE) and reactive ion etching (RIE) of a SiO2 in the plasma are investigated to achieve the goal. It was found that the aspect ratio and etching anisotropy decrease with increase of H-2 content in the feed during SiO2 etching in CF4 + H-2 plasma. The concentration of CF radical is insufficient to passivate the sidewalls completely. Meanwhile, the formation and subsequent growth of fluorocarbon film stop etching during one-dimensional PCE Of SiO2 at critical H-2 content in the feed. (C) 2003 Elsevier B.V. All rights reserved.