Our recent work on deposition and characterization of hydrogenated microcrystalline silicon (μ c-Si:H) thin films and silicon thin film solar cells prepared by RF-PECVD under high-pressure-depletion conditions is summarized in this paper. Several key issues are studied in detail: 1) process windows for device-quality μ c-Si:H thin films, 2) formation mechanism of amorphous silicon incubation layer and the effective methods to reduce the incubation layer thickness, 3) modification of crystalline fraction volume of intrinsic μ c-Si:H layers and its influence on the device performance of μ c-Si:H solar cells, 4) deposition of high conductive p-type μ c-Si:H window layers with high crystalline fraction volume, and the influence of p-layer on the device performance. After solving the above key issues, a high efficiency of 8.16% is obtained for μ c-Si:H sing-junction solar cell with intrinsic layer prepared by RF-PECVD under high-pressure-depletion conditions. When it is used as bottom cell in a-Si:H/μ c-Si:H tandem solar cell, the efficiency of tandem cell reaches 11.61%.