In microwave dry etching, the substrate/resist etching selectivity is controlled by adding a material, such as an additional gas, to the reaction gas plasma that heats the substrate with greater energy transfer efficiency than the resist. For example, a W substrate having a resist is etched with an SF.sub.6 reaction gas to which is added an Xe gas for generating incident ions that impinge the substrate with greater energy transfer than they do the resist. This produces a greater hot spot temperature for the substrate as compared with the resist to increase the substrate/resist etching selectivity. The hot spot temperature difference can be further effected by applying a bias potential to the substrate during the etching with an RF power supply.