Various embodiments herein relate to methods and apparatus for etching a recessed feature in a material on a substrate. For example, the methods may include (a) flowing a gas mixture into a processing chamber, where the gas mixture includes an etch component and a passivation component, and where the passivation component includes particular elements and/or species and/or is provided under particular conditions; (b) generating a plasma from the gas mixture in the processing chamber; and (c) exposing the substrate to the plasma and etching the recessed feature in the material on the substrate. In many cases, the material being etched on the substrate includes dielectric material and/or an electrically conductive material.