Patent ID: 8507334

Claim:
A method of manufacturing a semiconductor device comprising: emitting a laser beam having a first cross section perpendicular to a propagation direction of the laser beam; expanding the laser beam along a first direction to increase the cross section of the laser beam along the first direction; regulating an optical path length of the expanded laser beam along the first direction using a concave lens; condensing the laser beam along a second direction orthogonal to the first direction; and crystallizing a semiconductor film comprising amorphous silicon by irradiating the semiconductor film with the laser beam while relatively moving the surface with respect to the laser beam along a third direction orthogonal to the first direction wherein the laser beam has a second cross section on the surface, the second cross section being larger than the first cross section along the first direction and shorter than the first direction along the third direction; patterning the crystallized semiconductor film into a plurality of semiconductor lavers, each including a region to become a channel forming region of a thin film transistor.