A plasma reactor has been developed for dry reactive plasma etching and thin semiconductor film deposition. The system combines a multipolar magnetic field layer [1] for charged-particle confinement, and independently controlled substrate biasing. A large volume of dense (1011 cm-3), uniform, quiescent plasma is produced at low working pressure ( 1 mTorr). Anisotropic profiles can be etched into silicon in an SF6-O2 plasma with vertical etch rates ∼l um/min. In a pure silane plasma, good quality polycrystalline silicon films can be deposited at rates 1 to 10 Å/sec., at substrate temperatures 50° to 300° C.