The present invention provides a structure of a semiconductor device that realizes
low power consumption even where increased in screen size, and a method for manufacturing
the same. The invention forms an insulating layer, forms a buried interconnection
(of Cu, Au, Ag, Ni, Cr, Pd, Rh, Sn, Pb or an alloy thereof) in the insulating layer.
Furthermore, after planarizing the surface of the insulating layer, a metal protection
film (Ti, TiN, Ta, TaN or the like) is formed in an exposed part. By using the
buried interconnection in part of various lines (gate line, source line, power
supply line, common line and the like) for a light-emitting device or liquid-crystal
display device, line resistance is decreased.