Patent ID: 8785941

Claim:
A thin-film semiconductor device having a thin-film semiconductor element for driving a display device, the thin-film semiconductor device comprising: a substrate; a first gate line disposed on the substrate, through which a control signal is applied to the thin-film semiconductor element; a metal line above the substrate, the metal line crossing the first gate line; a first gate electrode of the thin-film semiconductor element, the first gate electrode extending from the first gate line; a second gate electrode on the first gate electrode; a gate insulating film on the second gate electrode; a semiconductor layer on the gate insulating film; a metal electrode on the semiconductor layer, the metal electrode extending from the metal line; an insulating layer provided, between the first gate line and the metal line, in a crossing area in which the first gate line and the metal line cross, to secure a distance between the first gate line and the metal line, the insulating layer being different from the gate insulating film; and a second gate line in a same layer as the second gate electrode, and on and along the first gate line in other than the crossing area, wherein the metal line is on the insulating layer, the second gate line and the second gate electrode are thicker than the first gate line and the first gate electrode, and an interface between the metal line and the insulating layer is positioned above a top surface of the second gate electrode, in a cross section above the first gate line and the second gate line and in a direction in which the first gate line and the second gate line extend.