E-book reader

Abstract

An e-book reader including a display panel having a thin film transistor with stable electrical characteristics is provided. Alternatively, an e-book reader capable of holding images for a long time is provided. Alternatively, a high-resolution e-book reader is provided. Alternatively, an e-book reader with low power consumption is provided. Display on the display panel of the e-book reader is controlled by a thin film transistor whose channel formation region is formed using an oxide semiconductor which is an intrinsic or substantially intrinsic semiconductor by removal of an impurity that might be an electron donor in the oxide semiconductor and has a larger energy gap than a silicon semiconductor.

1 . (canceled) 
     
     
         2 . A display device comprising a pixel, the pixel comprising:
 a first conductive layer over a substrate;   a first insulating layer over the first conductive layer;   an oxide semiconductor layer over the first insulating layer;   a second conductive layer over a portion of the oxide semiconductor layer;   a third conductive layer over a portion of the oxide semiconductor layer;   a second insulating layer over the oxide semiconductor layer, the second conductive layer and the third conductive layer;   a fourth conductive layer electrically connected to the second conductive layer;   a fifth conductive layer electrically connected to the third conductive layer; and   a sixth conductive layer over the second insulating layer,   wherein the first conductive layer includes a region configured to be a first gate electrode, and the sixth conductive layer includes a region configured to be a second gate electrode, and   wherein the sixth conductive layer contains a light-transmitting conductive oxide.   
     
     
         3 . The display device according to  claim 2 , wherein the first conductive layer has substantially a same potential as the sixth conductive layer. 
     
     
         4 . The display device according to  claim 2 , wherein the oxide semiconductor layer has a carrier concentration of 5×10 14 /cm 3  or lower. 
     
     
         5 . The display device according to  claim 2 , wherein the oxide semiconductor layer has an energy gap of 2 eV or higher. 
     
     
         6 . The display device according to  claim 2 , wherein the display device is incorporated in an e-book reader. 
     
     
         7 . A display device comprising a pixel, the pixel comprising:
 a first conductive layer over a substrate;   a first insulating layer over the first conductive layer;   an oxide semiconductor layer over the first insulating layer;   a second conductive layer over a portion of the oxide semiconductor layer;   a third conductive layer over a portion of the oxide semiconductor layer;   a second insulating layer over the oxide semiconductor layer, the second conductive layer and the third conductive layer;   a fourth conductive layer electrically connected to the second conductive layer;   a fifth conductive layer electrically connected to the third conductive layer; and   a sixth conductive layer over the second insulating layer,   wherein the first conductive layer includes a region configured to be a first gate electrode, and the sixth conductive layer includes a region configured to be a second gate electrode,   wherein the sixth conductive layer contains a light-transmitting conductive oxide, and   wherein the fourth conductive layer, the fifth conductive layer and the sixth conductive layer are provided over and in contact with the second insulating layer.   
     
     
         8 . The display device according to  claim 7 , wherein the first conductive layer has substantially a same potential as the sixth conductive layer. 
     
     
         9 . The display device according to  claim 7 , wherein the oxide semiconductor layer has a carrier concentration of 5×10 14 /cm 3  or lower. 
     
     
         10 . The display device according to  claim 7 , wherein the oxide semiconductor layer has an energy gap of 2 eV or higher. 
     
     
         11 . The display device according to  claim 7 , wherein the display device is incorporated in an e-book reader.