Abstract: An RF diode reactive ion etching (RIE) method and apparatus (20) include an evacuable reaction chamber (22) in which an anode electrode (76) and cathode electrode (30)are spaced-apart facing each other and defining a gap (78) between the electrodes. A substrate (40) to be etched is placed in thermal contact with the cathode. A magnet (70) behind the anode provides a magnetic field which is characterized by lines-of-force (80) extending continuously through the gap from one of the electrodes to the other. To etch the substrate the reaction chamber is evacuated, an etchant-gas is admitted into the gap at a predetermined low pressure, a plasma (79) including ions of the etchant gas is generated by applying RF power to the electrodes. The substrate is etched by etchant gas ions attracted from the plasma toward the substrate by a negative self-bias potential established on the cathode.