Making use of fabrication technology commonly employed in the manufacture of liquid crystal and semiconductor devices, but not previously applied to vacuum devices, the diamond-based backward wave oscillator (BWO) provides a miniature, energy efficient, electronically tunable and mass producible signal source in the sub mm wavelength regime. Fabricated within a shell of chemical vapor deposited (CVD) diamond for mechanical and thermal robustness, the BWO employs a novel biplanar interdigital slow wave circuit, which will be manufactured by utilizing a process developed at Genvac. Conventional silicon fabrication technology is used to form a negative of the desired structure, which serves as a mold for the deposition of the diamond. The diamond structure is then selectively metallized. The structure is formed in two halves and then accurately positioned and bonded using techniques routinely employed in the fabrication of liquid crystal displays. The device has been modeled extensively, and designs of the slow wave circuit, electron gun and collector for operation at 300 and 600 GHz have been completed. Fabrication of the 300 GHz device is in progress. It is estimated to weigh 29 gm, and, for operation over a 10% tuning range, the minimum output power is predicted to be 18 mW.