Poly-crystalline Si and Ge layers were grown at low temperatures on glass substrates by successive hydrogenation and annealing steps, with no need to any metal incorporation. Hydrogenation is performed in an RF-PECVD apparatus with different powers of hydrogen plasma and the annealing step is carried out in the same system in N2 ambient. This leads to formation of granular Si and Ge structures with average grain size of less than 100nm at temperatures as low as 250°C and 150°C, respectively. The effect of hydrogen plasma power at various temperatures on the crystallinity of the layers has been studied by SEM and TEM analyzes. Successive hydrogenation and annealing at respective temperatures of 150°C and 200°C for Ge layer and 300°C for Si layer would result in a device-quality polycrystalline Ge and Si layers which have been employed for fabrication of thin-film transistors. These TFTs show the mobility of 80cm2/Vs and 4cm2/Vs and ON/OFF ratio of more than 103 and 5×104 for Ge and Si, indicating the feasibility of this technique for applications in large-area electronics.