The crystallization of a-Si films, grown by low-pressure chemical vapor deposition and annealed by rapid thermal annealing (RTA), at 850 degrees C in conjunction with conventional heating at 600 degrees C for 6 h, has been studied using transmission electron microscopy. The results of RTA at 850 degrees C showed that the improvement of the poly-Si structure (large crystallites with low density of microtwins) was maximized for an annealing time of 150 s. The same results were also obtained by RTA at 850 degrees C with successive steps of 30 s duration each (5 X 30 s). A multiple-step annealing is sufficient to activate the movement of twin boundaries within the grains resulting in their annihilation. This process is comparable with the technology of growing good-quality poly-Si on low-cost glass substrates.