Thin film transistor, method for manufacturing the same, and semiconductor device
First Claim
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1. A transistor comprising:
- a gate electrode layer;
a gate insulating layer provided over the gate electrode layer;
an oxide semiconductor layer provided over the gate insulating layer;
a pair of conductive layers provided over the oxide semiconductor layer;
a metal oxide layer provided over the oxide semiconductor layer and between the pair of conductive layers, wherein the metal oxide layer contains a same metal element as the pair of conductive layers, and has a higher oxygen concentration than the pair of conductive layers;
a source electrode layer provided over one of the pair of conductive layers; and
a drain electrode layer provided over the other of the pair of conductive layers.
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Abstract
In a thin film transistor, an increase in off current or negative shift of the threshold voltage is prevented. In the thin film transistor, a buffer layer is provided between an oxide semiconductor layer and each of a source electrode layer and a drain electrode layer. The buffer layer includes a metal oxide layer which is an insulator or a semiconductor over a middle portion of the oxide semiconductor layer. The metal oxide layer functions as a protective layer for suppressing incorporation of impurities into the oxide semiconductor layer. Therefore, in the thin film transistor, an increase in off current or negative shift of the threshold voltage can be prevented.
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Citations
27 Claims
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1. A transistor comprising:
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a gate electrode layer; a gate insulating layer provided over the gate electrode layer; an oxide semiconductor layer provided over the gate insulating layer; a pair of conductive layers provided over the oxide semiconductor layer; a metal oxide layer provided over the oxide semiconductor layer and between the pair of conductive layers, wherein the metal oxide layer contains a same metal element as the pair of conductive layers, and has a higher oxygen concentration than the pair of conductive layers; a source electrode layer provided over one of the pair of conductive layers; and a drain electrode layer provided over the other of the pair of conductive layers. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A transistor comprising:
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a gate electrode layer; a gate insulating layer provided over the gate electrode layer; an oxide semiconductor layer provided over the gate insulating layer; a pair of conductive layers provided over the oxide semiconductor layer; a metal oxide layer provided over the oxide semiconductor layer and between the pair of conductive layers; a source electrode layer provided over one of the pair of conductive layers; and a drain electrode layer provided over the other of the pair of conductive layers. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A transistor comprising:
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a gate electrode layer; a gate insulating layer provided over the gate electrode layer; an oxide semiconductor layer provided over the gate insulating layer; a pair of conductive layers provided over the oxide semiconductor layer; a metal oxide layer provided over the oxide semiconductor layer and between the pair of conductive layers, wherein the metal oxide layer contains a same metal element as the pair of conductive layers; a source electrode layer provided over one of the pair of conductive layers; and a drain electrode layer provided over the other of the pair of conductive layers. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A transistor comprising:
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a gate electrode layer; a gate insulating layer provided over the gate electrode layer; an oxide semiconductor layer provided over the gate insulating layer; a pair of conductive layers provided over the oxide semiconductor layer; a metal oxide layer provided over the oxide semiconductor layer and between the pair of conductive layers, wherein the metal oxide layer has a higher oxygen concentration than the pair of conductive layers; a source electrode layer provided over one of the pair of conductive layers; and a drain electrode layer provided over the other of the pair of conductive layers. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification