Patent ID: 7777226

Claim:
A polycrystalline silicon thin film to be used in display devices, the polycrystalline silicon thin film having been formed by irradiating an amorphous silicon thin film with a laser beam through a mask comprising a plurality of opaque dots, the polycrystalline silicon thin film comprising primary grain boundaries beginning and ending at regions corresponding to the opaque dots of the mask so that adjacent primary grain boundaries of the primary grain boundaries are not parallel to each other and do not contact each other; wherein a minimum area surrounded by the primary grain boundaries and the regions corresponding to the opaque dots of the mask is larger than 1 μm 2 , wherein the mask further comprises: a first rectangular transparent region in which all of the opaque dots are disposed; and a second rectangular transparent region separated from the first rectangular transparent region by a non-transparent region, the second rectangular transparent region not having any opaque dots disposed therein.