Intrinsic stress in diamond films fabricated by hot filament chemical vapor deposition was investigated as a function of deposition temperature, CH4 concentration, and positive bias voltage. The intrinsic stress in the diamond film was tensile between 810 and 980 degrees C. The minimum tensile stress existed at 880 degrees C. The relationship between tensile intrinsic stress and deposition temperature was explained by the nondiamond phase and crystallite size. The tensile intrinsic stress decreased almost linearly with CH4 concentration in the range of 0.4%-1.2%. Applying +50 V to the Si substrate, the tensile intrinsic stress was reduced from 2.4 to 0.7 GPa without any change in the quality of the diamond film. This relaxation was attributed to the beta-SiC buffer layer formed by electron bombardment onto the Si substrate.