Thin film transistor having a two-layer semiconductor, manufacturing method therefor, and display apparatus using the same

Abstract

A transistor is constituted of a gate electrode 2 , a gate insulation layer 3 , a semiconductor layer 4 formed of an amorphous oxide, a source electrode 5 , a drain electrode 6 and a protective layer 7 . The protective layer 7 is provided on the semiconductor layer 4 in contact with the semiconductor layer 4 , and the semiconductor layer 4 includes a first layer at least functioning as a channel layer and a second layer having higher resistance than the first layer. The first layer is provided on the gate electrode 2 side of the semiconductor layer 4 and the second layer is provided on the protective layer 7 side of the semiconductor layer 4.

1 . A thin film transistor comprising a gate electrode, a gate insulation layer, a semiconductor layer formed of an oxide semiconductor, a source electrode, a drain electrode and a protective layer,
 wherein the protective layer is provided on the semiconductor layer in contact with the semiconductor layer, and   wherein the semiconductor layer includes a first layer at least functioning as a channel layer and a second layer having higher resistance than the first layer, the second layer being provided on the protective layer side of the semiconductor layer, and the second layer has a mass density not larger than the mass density of the first layer.   
     
     
         2 . The thin film transistor according to  claim 1 , wherein the second layer has a mass density not larger than 90% of the mass density in the crystal state of a material constituting the second layer. 
     
     
         3 . The thin film transistor according to  claim 1 , wherein the semiconductor layer is formed of an amorphous oxide semiconductor containing at least one of In, Zn and Ga. 
     
     
         4 . The thin film transistor according to  claim 1 , wherein the first layer is provided on the gate electrode side of the semiconductor layer. 
     
     
         5 . The thin film transistor according to  claim 1 , wherein the semiconductor layer is oxidized more deeply than the depth of damage the semiconductor layer receives when the protective layer is formed.