This work describes the microstructure and mechanical properties of B-C-N-H films synthesized by medium frequency magnetron sputtering from a boron target in a N-2 + CH4 + Ar gas mixture. The increase in the CH4 flow rate increases the carbonaceous compound species, causes the increase of the C atomic concentration and promotes the formation of sp(3)-hybridized carbon. The change of hardness with the CH4 flow rate had a relationship with the residual stress. The coefficient of friction was reduced approximately from 0.8 to 0.18, and wear resistance was considerably improved by increasing the flow of CH4 gas component from 0 to 40 sccm. The change of films' hardness was discussed and attributed primarily to the internal defects and bonding characteristics, while the superior tribological properties of the films could be assigned to the formation of sp(3)-hybridized carbon and the C-H bonding. (C) 2009 Elsevier B. V. All rights reserved.