High‐density (≤5×1011 cm−3) magnetically enhanced discharges operated at low pressure (1 mTorr) with low additional rf‐induced dc bias (≤−100 V) on the sample enable self‐aligned dry etchfabrication of a wide variety of III–V devices and circuits for lightwave digital and microwave applications. In many cases the ohmic metal contacts are used as the etch masks in order to minimize parasitic resistances and capacitances resulting from the lateral separation of these contacts. Applications range from formation of shallow mesas (≤400 Å) on high electron mobility transistors to etching of through‐wafer vias (∼100 μm). The chemistries employed for these fabrication steps are reviewed, together with examples of processing sequences for heterojunctionbipolar transistors and novel microdisk lasers that may form the basis of future electronic and microphotonic circuits.