Laser crystallization of amorphous semiconductor thin films and laser epitaxy, particularly of silicon, are presented. The theoretical background of nucleation and growth is discussed with respect to applications. It is demonstrated that short pulse laser irradiation of amorphous films leads to fine grains in the 10 nm to 1 mu m range independent of the semiconductor. With longer pulses in the ms range or by scanning the beam of a cw laser, large crystals in the 100 mu m range can be produced in the case Si or Ge on glass substrates. Epitaxial thickening of large-grained Si layers can be achieved by short-pulse laser melting during further deposition of a-Si. (c) 2005 Elsevier B.V. All rights reserved.