Intrinsic hydrogenated microcrystalline silicon films have been deposited by Plasma Enhanced Chemical Vapor Deposition using highly diluted SiH4 in H-2 discharges, aiming at the increase of the deposition rate. Following a systematic optimization of the main process parameters, an increase of the film growth rate up to 7.5 A/s has been achieved, from 1 Torr 6% SiH4 in H-2 dust-free discharges at a frequency of 30 MHz. The experimental results are combined to a mass transfer model that can very well predict the deposition rate, for revealing the main reasons leading to the fast growth of muc-Si:H.