This paper proposes the effects of chamber pressures on the passivation layer of hydrogenated nano-crystalline silicon (nc-Si:H) mixed-phase thin film using microwave annealing (MWA) to achieve a high-quality thin film. The use of 40.68 MHz very-high-frequency plasma-enhanced chemical vapor deposition (VHFPECVD) deposited the nc-Si:H mixed-phase thin film on the top and bottom of the n-type crystalline silicon substrate. The chamber pressures (0.2, 0.4, 0.6, and 0.8 Torr) of the VHFPECVD were critical factors in controlling the carrier lifetime of the symmetric structure. By using the VHFPECVD to deposit the nc-Si:H and using the MWA to enhance the quality of the symmetric structure, the deposited nc-Si:H’s properties of a crystalline volume fraction of 29.6%, an optical bandgap of 1.744 eV, and a carrier lifetime of 2942.36 μs were well achieved, and could be valuable in thin-film solar-cell applications.