The plasma parameters for the fast deposition of highly crystallized microcrystalline silicon (µc-Si) films with low defect density are presented using a high-density and low-temperature SiH4-H2 mixture microwave plasma. A very high deposition rate of $\sim $65 Å/s was achieved for a SiH4 concentration of 67% diluted in H2 with a high Raman crystallinity Ic/Ia > 2.5 and a low defect density of 1−2 × 1016 cm−3 by adjusting the plasma conditions. Contrary to the case of a conventional rf plasma, the defect density of the µc-Si films strongly depends on substrate temperature, Ts, and increases with increasing Ts even if Ts is below 300 °C. This indicates that the real temperature at the growing surface is higher than the monitored value. A sufficient supply of deposition precursors such as SiH3 at the growing surface under an appropriate ion bombardment is effective for the fast deposition of highly crystallized µc-Si films as well as for the suppression of the amorphous incubation and transition interface layers at the initial growth stage.