The guiding principles for obtaining device-grade hydrogenated amorphous silicon (a-Si:H) films with high deposition rate on large-area substrates by catalytic chemical vapor deposition (Cat-CVD) are presented. The most important points are controlling both the heat flow and the atomic H. Other points of note are the suppression of silicide formation on the catalyzer and control of the gas flow. Solar cells and thin-film transistors using a-Si:H films thus obtained show excellent device performance. Large-area deposition, high deposition rate and high efficiency of gas use are also promising for the application of Cat-CVD a-Si:H films to these devices.