Heavily boron-doped diamond films are synthesized by the hot-filament chemical vapor deposition method under the gas mixtures of H-2, CH4 and trimethyl borate. The measurement results of scanning electron microscopy, Raman spectroscopy, X-ray diffractometer and electrical properties showed the morphologies, microstructures, carrier concentration and superconducting transition temperature for as-grown diamond films were dependent on the change of growth pressure, and specially its carrier concentrations could be adjusted from 1019 to 1021 cm (3) by increasing growth pressures from 2.5 to 5 kPa. And further, the effects of growth pressure on the film microstructural property and the doping level dependence of the superconducting transition temperature were discussed. (C) 2009 Elsevier B.V. All rights reserved.