Hydrogenated silicon films were deposited by RF sputtering with various hydrogen partial pressures. The samples were examined by infrared absorption spectroscopy, transmission electron microscopy and optical absorption techniques, in addition to dark conductivity measurements. For low hydrogen pressure ratios ( less than or equal to 20%), the deposited hydrogenated films were completely amorphous, but they increasingly crystallize for increasingly higher ratio of hydrogen pressure. Beside an appropriate value of the optical band gap, the conductivity improved by more than eight orders of magnitude, from similar to 10(-11) Omega(-1) cm(-1) for the amorphous phase to similar to 10(-3) Omega(-1) cm-l for the most crystalline one. This latter value and the corresponding low activation energy (0.13 eV) are explained in terms of a thermally-assisted tunnelling process.