THIN FILM TRANSISTOR AND DISPLAY DEVICE HAVING THE THIN FILM TRANSISTOR

摘要

A thin film transistor includes a gate electrode, a gate insulating layer covering the gate electrode, a microcrystalline semiconductor layer over the gate insulating layer, an amorphous semiconductor layer over the microcrystalline semiconductor layer, source and drain regions over the amorphous semiconductor layer, source and drain electrodes in contact with and over the source and drain regions, and a part of the amorphous semiconductor layer overlapping with the source and drain regions is thicker than a part of the amorphous semiconductor layer overlapping with a channel formation region. The side face of the source and drain regions and the side face of the amorphous semiconductor form a tapered shape together with an outmost surface of the amorphous semiconductor layer. The taper angle of the tapered shape is such an angle that decrease electric field concentration around a junction portion between the source and drain regions and the amorphous semiconductor layer.