Patent ID: 8089071

Claim:
A thin film semiconductor device comprising: a semiconductor thin film having an active region turned into a polycrystalline region through irradiation with an energy beam; and a gate electrode provided to traverse the active region; wherein successive crystal grain boundaries extend along the gate electrode in a channel part that is a portion of the active region overlapping with the gate electrode, the crystal grain boundaries traverse the channel part and are provided cyclically in a channel length direction, and crystal grains each having a crescent shape are provided between the crystal grain boundaries and are arranged along an extension direction of the crystal grain boundaries, the crescent shape having a curved convex side that is convex in the extension direction of the crystal grain boundaries and a curved concave side opposite to the convex side, wherein the number of the crystal grain boundaries provided in the channel part is set to a predetermined number greater than or equal to 17 and less than or equal to 50.