Amorphous hydrogenated carbon (a-C:H) film have been deposited by RF magnetron sputtering system in H-2/He plasma. We investigated the effects of the gas pressure (p(1)) to films deposited in a wide region of relative hydrogen gas flow rate. The growth rate of the films at p(t)=53.2 Pa was the highest. The bonding hydrogen concentration (n(H)) and the optical gap of the film at higher p(t) were higher. Moreover, the film with high n(H) had high optical gap. These results indicate that the film with the high optical gap can be deposited at low R-H by using high pt. (c) 2005 Published by Elsevier B.V.