Amorphous films (a-C:H:Si and a-C:H:Si:O) were grown in a vacuum chamber containing a hot filament on substrates held on a copper plate to which a bias voltage could be applied. This modified hot-filament chemical vapor deposition process was used to fabricate various types of amorphous thin film from mixtures of tetramethylsilane (TMS) or hexamethyldisiloxane (HMDSO) diluted in argon or argon/nitrogen mixtures. Electrical characteristics of the process, deposition rates, and film structures were investigated as a function of the deposition parameters, particularly the proportion of nitrogen in the chamber feed. For film characterization, transmission infrared spectroscopy (IRS) was employed. Without a significant substrate current, deposition rates were negligible. Thus, electron impact fragmentation of the monomer molecules is a key process in film deposition using this technique. The method shows promise and versatility for the fabrication of a wide range of amorphous films, including, for example, a-C:H and a-C:H:O.