Semiconductor device

Abstract

In the present invention, a thin film transistor is formed on a plastic film substrate ( 1 ) having anisotropy of thermal shrinkage rate or coefficient of thermal expansion in in-plane directions of the substrate. A channel is formed such thatthe direction ( 7 ) in which the thermal shrinkage rate or the coefficient of thermal expansion of the substrate is largest is nonparallel tothe direction ( 8 ) of a current flowing through the channel of the thin film transistor. Then, a thin film transistor having stable and uniform electrical characteristics, which is formed on the plastic film substrate, is provided.

1 . A semiconductor device formed on a substrate surface of a substrate having anisotropy of either thermal shrinkage rate or coefficient of thermal expansion in in-plane directions of the substrate,
 wherein the direction in which either the thermal shrinkage rate or the coefficient of thermal expansion of the substrate is largest is nonparallel to the direction of a current flowing through the semiconductor device.   
   
   
       2 . A semiconductor device formed on a substrate surface of a substrate having anisotropy of either thermal shrinkage rate or coefficient of thermal expansion in in-plane directions of the substrate,
 wherein a direction in which either the thermal shrinkage rate or the coefficient of thermal expansion of the substrate is smallest is parallel to the direction of a current flowing through the semiconductor device.   
   
   
       3 . A semiconductor device according to  claim 1 , wherein the semiconductor device comprises an active layer for which a transparent oxide semiconductor containing In, Ga, Zn, and O is used. 
   
   
       4 . A semiconductor device according to  claim 1 , wherein the substrate is composed of polymer resin. 
   
   
       5 . A semiconductor device according to  claim 1 , wherein the substrate is of a plastic film obtained by melt-processing a thermoplastic resin in a sheet shape and biaxially stretching the thermoplastic resin in longitudinal and transverse directions. 
   
   
       6 . A semiconductor device according to  claim 1 , wherein the semiconductor device is of a thin film transistor.