Patent ID: 8012841

Claim:
A laser annealing method of reforming an amorphous semiconductor film into a polycrystalline semiconductor film by concentrating a laser beam emitted from a solid laser source into a rectangular laser beam on a surface of the amorphous semiconductor film and applying the rectangular laser beam thereto while moving the rectangular laser beam relative to the amorphous semiconductor film in a short-side direction of the rectangular laser beam, comprising: uniformizing an energy distribution in the short-side direction of the rectangular laser beam by dividing the laser beam into divided laser beams through a light guide and focusing the divided laser beams through a Y-direction end transferring optical system including two cylindrical lenses; and applying the rectangular laser beam to the amorphous semiconductor film, wherein a Y-direction coherence reducing optical system, which includes a first transparent glass plate and a second transparent glass plate, is provided between the two cylindrical lenses, and wherein a length of the first transparent glass plate is different from a length of the second transparent glass plate.