Semiconductor device and method for manufacturing the same
First Claim
1. A semiconductor device comprising:
- a gate electrode layer over a substrate having an insulating surface;
a gate insulating layer over the gate electrode layer;
an oxide semiconductor layer including a channel formation region over the gate insulating layer;
a buffer layer over the oxide semiconductor layer; and
source and drain electrode layers over the buffer layer,wherein the buffer layer includes a first region which is in contact with one of the source and drain electrode layers,wherein the buffer layer includes a second region which is in contact with the channel formation region,wherein the first region has higher electrical conductivity than the channel formation region, andwherein the second region has lower electrical conductivity than the channel formation region.
1 Assignment
0 Petitions
Accused Products
Abstract
It is an object to provide a highly reliable semiconductor device including a thin film transistor with stable electric characteristics. In a semiconductor device including an inverted staggered thin film transistor whose semiconductor layer is an oxide semiconductor layer, a buffer layer is provided over the oxide semiconductor layer. The buffer layer is in contact with a channel formation region of the semiconductor layer and source and drain electrode layers. A film of the buffer layer has resistance distribution. A region provided over the channel formation region of the semiconductor layer has lower electrical conductivity than the channel formation region of the semiconductor layer, and a region in contact with the source and drain electrode layers has higher electrical conductivity than the channel formation region of the semiconductor layer.
-
Citations
39 Claims
-
1. A semiconductor device comprising:
-
a gate electrode layer over a substrate having an insulating surface; a gate insulating layer over the gate electrode layer; an oxide semiconductor layer including a channel formation region over the gate insulating layer; a buffer layer over the oxide semiconductor layer; and source and drain electrode layers over the buffer layer, wherein the buffer layer includes a first region which is in contact with one of the source and drain electrode layers, wherein the buffer layer includes a second region which is in contact with the channel formation region, wherein the first region has higher electrical conductivity than the channel formation region, and wherein the second region has lower electrical conductivity than the channel formation region. - View Dependent Claims (6, 7, 10, 13, 16, 17)
-
-
2. A semiconductor device comprising:
-
a gate electrode layer over a substrate having an insulating surface; a gate insulating layer over the gate electrode layer; a first oxide semiconductor layer including a channel formation region over the gate insulating layer; a second oxide semiconductor layer over the first oxide semiconductor layer; and source and drain electrode layers over the second oxide semiconductor layer, wherein the second oxide semiconductor layer includes a metal selected from group consisting of titanium, molybdenum, manganese and combination thereof, wherein the second oxide semiconductor layer includes a first region which is in contact with one of the source and drain electrode layers, wherein the second oxide semiconductor layer includes a second region which is in contact with the channel formation region, wherein the first region has higher electrical conductivity than the channel formation region, and wherein the second region has lower electrical conductivity than the channel formation region. - View Dependent Claims (3, 4, 11, 14, 18, 19)
-
-
5. A semiconductor device comprising:
-
a gate electrode layer over a substrate having an insulating surface; a gate insulating layer over the gate electrode layer; an oxide semiconductor layer including a channel formation region over the gate insulating layer; a buffer layer over the oxide semiconductor layer; and source and drain electrode layers over the buffer layer, wherein in the buffer layer, a first region which is in contact with one of the source and drain electrode layers is a metal region and a second region which is in contact with the channel formation region of the oxide semiconductor layer is a metal oxide region, and wherein the metal oxide region has lower electrical conductivity than the channel formation region of the oxide semiconductor layer. - View Dependent Claims (8, 9, 12, 15, 20, 21)
-
-
22. A semiconductor device comprising a transistor, the transistor comprising:
-
a first oxide semiconductor layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode over the second oxide semiconductor layer; and a drain electrode over the second oxide semiconductor layer, wherein the first oxide semiconductor layer includes a first region as a channel formation region, wherein the second oxide semiconductor layer includes a second region overlapping with the first region, wherein the second oxide semiconductor layer includes a third region in contact with the source electrode, wherein the second oxide semiconductor layer includes a fourth region in contact with the drain electrode, wherein the first region has a first electrical conductivity, wherein the second region has a second electrical conductivity, wherein the third region has a third electrical conductivity, wherein the fourth region has a fourth electrical conductivity, wherein the second electrical conductivity is lower than the first electrical conductivity, wherein the third electrical conductivity is higher than the second electrical conductivity, and wherein the fourth electrical conductivity is higher than the second electrical conductivity. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
-
-
31. A semiconductor device comprising a transistor, the transistor comprising:
-
a first oxide semiconductor layer; a second oxide semiconductor layer over the first oxide semiconductor layer; a source electrode over the second oxide semiconductor layer; and a drain electrode over the second oxide semiconductor layer, wherein the first oxide semiconductor layer includes a first region as a channel formation region, wherein the second oxide semiconductor layer includes a second region overlapping with the first region, wherein the second oxide semiconductor layer includes a third region in contact with the source electrode, wherein the second oxide semiconductor layer includes a fourth region in contact with the drain electrode, wherein the first region has a first electrical conductivity, wherein the second region has a second electrical conductivity, wherein the third region has a third electrical conductivity, wherein the fourth region has a fourth electrical conductivity, wherein the second electrical conductivity is lower than the first electrical conductivity, wherein the third electrical conductivity is higher than the second electrical conductivity, wherein the fourth electrical conductivity is higher than the second electrical conductivity, and wherein the second region contains oxygen at a higher concentration than the third region and the fourth region. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39)
-
Specification