The two-dimensional profiles of etched grooves have been calculated as a function of the size of masks and the ion flux of bombarding ions. The model includes processes of adsorption of chemically active species arriving from plasma, heterogeneous chemical reactions (formation volatile compounds on the surface), thermal desorption, physical sputtering, activation of surface atoms by the bombarding ions and ion beam activated desorption. Special interest is concentrated on the etching anisotropy, lateral etching and aspect ratio with dependence on the size of mask. It is shown that ion irradiation changes etching kinetics and etching anisotropy. The main role of ions is related to the activation of heterogeneous reactions. It is shown that the profiles of the etched grooves can be modified by changing irradiation conditions and geometry of masks. Calculated results are qualitatively in good correspondence with ones obtained experimentally.