Patent ID: 8624237
Filing Date: 2014-01-07
Classification: G02F,G09G,H01L

Abstract:
1. A semiconductor device including a thin film transistor, the thin film transistor comprising: a gate electrode layer; a gate insulating layer over the gate electrode layer; a semiconductor layer over the gate insulating layer; a first n-type buffer layer and a second n-type buffer layer over the semiconductor layer; a source electrode layer over the first n-type buffer layer, and a drain electrode layer over the second n-type buffer layer; a third buffer layer between the semiconductor layer and the first n-type buffer layer; and a fourth buffer layer between the semiconductor layer and the second n-type buffer layer, wherein each of the semiconductor layer, the first n-type buffer layer and the second n-type buffer layer comprises oxide semiconductor containing indium, gallium, and zinc, wherein each of the first n-type buffer layer and the second n-type buffer layer has higher carrier concentration than the semiconductor layer, wherein each of the first n-type buffer layer and the second n-type buffer layer contains one selected from the group consisting of magnesium, aluminum and titanium, and wherein each of the third buffer layer and the fourth buffer layer has a carrier concentration which is higher than that of the semiconductor layer and lower than that of each of the first n-type buffer layer and the second n-type buffer layer.