The comparative study of HCl and HBr plasma chemistries was carried out using plasma modeling. It was found that both gas systems are characterized by similar reaction schemes and exhibit only the quantitative differences in kinetics of both neutral and charged species. For one and the same ranges of electron temperature and electron density, the important features of the HBr plasma are: (1) higher dissociation degree and Br atom density; (2) higher electronegativity; and (3) higher efficiency of the physical etching pathway.