Patent ID: 8212254

Claim:
A manufacturing method of a thin film transistor by using a CW laser light or a pseudo CW laser light, comprising: forming an amorphous semiconductor film over a substrate having an insulating surface; spatially modulating a light intensity of a linear-shaped laser light with an optical intensity modulator that periodically modulates in a major axis direction of the laser light; and irradiating the amorphous semiconductor film with the laser light to form a polycrystalline semiconductor film including a crystal band that grows in a scanning direction of the laser light by completely melting the amorphous semiconductor film, wherein the optical intensity modulator is a phase-shift mask having a trench in a direction that tilts off a direction parallel to a scanning direction of the laser light by a certain angle, wherein a value of light intensity that is periodically modulated in the major axis direction of the laser light has a maximum value and a minimum value in the major axis direction, and wherein the certain angle is adjusted so that the minimum value is more than or equal to 80% of the maximum value.