Semiconductor devices and methods of manufacture
A device includes a carbon nanotube having a channel region and dopant-free source/drain regions at opposite sides of the channel region, a first metal oxide layer interfacing a first one of the dopant-free source/drain regions of the carbon nanotube, a second metal oxide layer interfacing a second one of the dopant-free source/drain regions of the carbon nanotube and a gate structure over the channel region of the carbon nanotube, and laterally between the first metal oxide layer and the second metal oxide layer.
1 . A device, comprising:
a substrate;
a carbon nanotube over the substrate having source/drain regions and a channel region between the source/drain regions;
band-edge shift inducing layers respectively in contact with the source/drain regions of the carbon nanotube, wherein valence bands in the source/drain regions of the carbon nanotube are shifted from valence band edges in the channel region of the carbon nanotube;
a gate structure over the channel region of the carbon nanotube; and
an auxiliary band-edge shift inducing layer in contact with a source/drain extension region of the carbon nanotube, wherein the source/drain extension region is between the channel region and one of the source/drain regions.
2 . The device of claim 1 , wherein the band-edge shift inducing layers are metal oxide layers.
3 . The device of claim 1 , wherein the source/drain regions of the carbon nanotube are surrounded by the band-edge shift inducing layers.
4 . The device of claim 1 , wherein the band-edge shift inducing layers are metal oxide layers has a work function greater than 5 eV.
5 . The device of claim 1 , wherein the band-edge shift inducing layers are metal oxide layers has a work function less than 5 eV.
6 . The device of claim 1 , wherein the source/drain regions of the carbon nanotube are free of dopants.
7 . The device of claim 1 , further comprising:
a metal contact over the band-edge shift inducing layer.
8 . The device of claim 1 , wherein the auxiliary band-edge shift inducing layer is a metal oxide layer.
9 . The device of claim 1 , wherein the auxiliary band-edge shift inducing layer extends between one of the band-edge shift inducing layers and the gate structure in a cross-sectional view.
10 . A device, comprising:
a carbon nanotube having a channel region and dopant-free source/drain regions at opposite sides of the channel region;
a first metal oxide layer interfacing a first one of the dopant-free source/drain regions of the carbon nanotube;
a second metal oxide layer interfacing a second one of the dopant-free source/drain regions of the carbon nanotube; and
a gate structure over the channel region of the carbon nanotube, and laterally between the first metal oxide layer and the second metal oxide layer.
11 . The device of claim 10 , wherein the dopant-free source/drain regions have p-type behavior induced by the first metal oxide layer and the second metal oxide layer.
12 . The device of claim 10 , wherein the dopant-free source/drain regions have n-type behavior induced by the first metal oxide layer and the second metal oxide layer.
13 . The device of claim 10 , wherein the first metal oxide layer and the second metal oxide layer have a work function greater than 5 eV.
14 . The device of claim 10 , wherein the first metal oxide layer and the second metal oxide layer have a work function less than 5 eV.
15 . The device of claim 10 , further comprising:
a first metal contact over the first metal oxide layer; and
a second metal contact over the second metal oxide layer.
16 . The device of claim 15 , wherein the first metal contact and the second metal contact are in contact with the dopant-free source/drain regions of the carbon nanotube, respectively.
17 . A method, comprising:
forming a carbon nanotube over a substrate;
forming a first metal oxide layer over and a second metal oxide layer over source/drain regions of the carbon nanotube; and
forming a gate structure over a channel region of the carbon nanotube and between the first metal oxide layer and the second metal oxide layer.
18 . The method of claim 17 , further comprising:
forming an interlayer dielectric (ILD) layer over the carbon nanotube; and
etching the ILD layer to form contact holes exposing the source/drain regions of the carbon nanotube, wherein the first metal oxide layer and the second metal oxide layer are formed in the contact holes.
19 . The method of claim 18 , wherein the first metal oxide layer and the second metal oxide layer have top surfaces lower than a top surface of the ILD layer.
20 . The method of claim 17 , further comprising:
forming an auxiliary band-edge shift inducing layer over a source/drain extension region of the carbon nanotube, wherein the source/drain extension region is between the channel region and one of the source/drain regions.