A method of manufacturing a semiconductor characterized in that, in polycrystallizing an amorphous silicon thin film formed on a substrate through an annealing process, the amorphous silicon thin film has a plane area of 1000 μm2 or less. A thin-film transistor characterized by comprising an active silicon film which is formed of a plurality of island-like regions arranged in parallel to each other, each of the island-like regions being formed of a polycrystal silicon thin film having a plane area of 1000 μm2 or less. A method of manufacturing a thin-film transistor comprising the steps of: forming an amorphous silicon thin film on a substrate; processing the amorphous silicon thin film into a plurality of island-like regions each having a plane area of 1000 μm2 or less; polycrystallizing an amorphous silicon thin film that forms the island-like regions through an annealing process; and forming a thin-film transistor having at least one of the plurality of island-like regions as an active silicon layer.