Hydrogenated nanocrystalline silicon (nc-Si:H) films were directly deposited by using 13.56 MHz plasma-enhanced chemical vapor deposition at a substrate temperature of 260 degrees C with highly hydrogen (H-2) diluted silane (SiH4) gases. The nc-Si:H film showed a high Raman crystalline volume fraction (X-C similar to 85%) and low oxygen concentration (C-O similar to 1.5 X 10(17) at./cm(3)). The formation of high-quality nc-Si:H is explained in terms of the effective roles of atomic hydrogen in the plasma. Top-gate staggered n-channel thin-film transistors (TFTs) adopting 90 - 100 nm nc-Si:H channel and similar to 300 nm hydrogenated amorphous silicon oxide (a-SiOx) gate dielectric layers showed a field-effect mobility (mu(FE)) of similar to 150 cm(2)/V s, a threshold voltage (V-T) of similar to 2 V, a subthreshold slope (S) of -0.23 V/dec, and an on/off current ratio of more than 10(6). The TFT performance reported here offers promise for the total integration of peripheral electronics for active-matrix flat panel systems. (c) 2006 American Vacuum Society.