The growth of diamond films on (001) Si substrates by bias‐controlled chemical vapor deposition is described. The film quality as judged by Raman spectroscopy and scanning electron microscopy depends strongly on the biasing conditions. Under low current reverse bias conditions, highly facetted cubo‐octahedral diamond growth exhibiting a single sharp Raman line at 1332 cm−1was obtained, while biasing in high current conditions which created a plasma resulted in multiply twinned, microcrystalline growth incorporatingsp2‐bonded carbon into the diamond film.