Patent ID: 7868267

Claim:
A manufacturing method of a semiconductor device comprising: forming a semiconductor film over an insulating surface; forming a plurality of laser beams simultaneously by using optical systems, wherein the plurality of laser beams are elliptical laser beams or rectangular laser beams; irradiating the plurality of laser beams to at least a portion and another portion of the semiconductor film simultaneously while the semiconductor film is moved in a first direction; moving the semiconductor film in a second direction; and irradiating the plurality of laser beams to subsequent latter portions simultaneously while the semiconductor film is moved in a direction reverse to the first direction, wherein the plurality of laser beams are parallel to one another, wherein incident angles of the plurality of the laser beams with respect to an irradiating face of the semiconductor film are the same and fixed acute angles, wherein the plurality of laser beams are transmitted through the semiconductor film and reflected on a reflecting plate under the semiconductor film, and wherein the plurality of laser beams are incident to the semiconductor film again.