A thin film made of silicon or another IV-group crystals (crystals and mixed
crystals
of C, Ge, Sn, and Pb) is twice scanned with a laser beam moving in two lateral
directions in which crystal grains grow larger in order to form high-quality polycrystals
in exact positions in the thin film, while defects uncontrollable by the prior
arts are being reduced significantly, to realize a high-quality TFT device. The
laser-scanning directions are defined by the crystallization face orientations.
