Patent ID: 8546810

Claim:
A thin film transistor comprising: a first wiring layer; a gate insulating layer that covers the first wiring layer; a pair of first impurity semiconductor layers over the gate insulating layer, the pair of first impurity semiconductor layers partly overlapping with the first wiring layer; a semiconductor layer between the pair of first impurity semiconductor layers, the semiconductor layer being in contact with the pair of first impurity semiconductor layers; a pair of second impurity semiconductor layers, wherein one of the pair of second impurity semiconductor layers covers at least an outer end portion of one of the pair of first impurity semiconductor layers, wherein the other of the pair of second impurity semiconductor layers covers at least an outer end portion of the other of the pair of first impurity semiconductor layers, and wherein the pair of second impurity semiconductor layers is spaced from and does not overlap the semiconductor layer; and a second wiring layer over at least one of the pair of second impurity semiconductor layers.