The loading effect during plasmochemical etching (PCE) of silicon in a CF4 + O-2 plasma is considered. The loading effect is considered including homogeneous reactions of generation and recombination of chemically active species. The model of chemical composition of CF4 + O-2 plasma is related to the model of plasmochemical etching of silicon in CF4 + O-2 plasma to achieve the goal. Using the proposed model the influence of etchable surface area on concentration of F atoms in the plasma and etching rate was determined. It was found that the loading effect is more pronounced at low O-2 content in the feed. At low values of the etchable surface area, conversion of F atoms to the reaction products decreases with the increase of O-2 content in the feed. (C) 2003 Elsevier Science B.V. All rights reserved.