Production method for thin-film semiconductor

A method of fabricating a polycrystalline silicon film on a substrate by crystallizing an amorphous silicon film on the substrate, the method comprising, sequentially:

• focusing a laser beam of visible light into a line shape having a length and a width, with a Gaussian intensity distribution along the width, on an amorphous silicon film;
• scanning the laser beam of visible light across the amorphous silicon film in a direction perpendicular to the length of the line shape, so the laser beam of visible light scans a first area including first and second end regions, lying along sides of the first area that are perpendicular to the length of the line shape, and converts amorphous silicon in the first area into polycrystalline silicon;
• focusing a laser beam of ultraviolet light on the first end region;
• scanning the laser beam of ultraviolet light across the first end region in the direction perpendicular to the length of the line shape to convert the first end region into amorphous silicon;
• focusing the laser beam of visible light on a line adjacent to the first area and overlapping the first end region;
• and
• scanning the laser beam of visible light in the direction perpendicular to the length of the line shape to convert amorphous silicon into polycrystalline silicon in a second area adjacent to the first area.