The drain voltage of a transistor is determined depending on the driving voltage of an element connected to the transistor. With downsizing of a transistor, intensity of the electric field concentrated in the drain region is increased, and hot carriers are easily generated. An object is to provide a transistor in which the electric field hardly concentrates in the drain region. Another object is to provide a display device including such a transistor. End portions of first and second wiring layers having high electrical conductivity do not overlap with a gate electrode layer, whereby concentration of an electric field in the vicinity of a first electrode layer and a second electrode layer is reduced; thus, generation of hot carriers is suppressed. In addition, one of the first and second electrode layers having higher resistivity than the first and second wiring layers is used as a drain electrode layer.