SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME
First Claim
1. A semiconductor device comprising:
- a gate electrode over a substrate;
a gate insulating layer over the gate electrode;
a source electrode and a drain electrode over the gate insulating layer;
a first oxide semiconductor region over the source electrode and the drain electrode; and
a second oxide semiconductor region over the first oxide semiconductor region,wherein part of the first oxide semiconductor region is in contact with the gate insulating layer and side surface portions of the source electrode and the drain electrode,wherein an electrical conductivity of the second oxide semiconductor region is lower than an electrical conductivity of the first oxide semiconductor region, andwherein the first oxide semiconductor region is electrically connected with the source electrode and the drain electrode.
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Accused Products
Abstract
An object is, in a thin film transistor in which an oxide semiconductor is used as an active layer, to prevent change in composition, film quality, an interface, or the like of an oxide semiconductor region serving as an active layer, and to stabilize electrical characteristics of the thin film transistor. In a thin film transistor in which a first oxide semiconductor region is used as an active layer, a second oxide semiconductor region having lower electrical conductivity than the first oxide semiconductor region is formed between the first oxide semiconductor region and a protective insulating layer for the thin film transistor, whereby the second oxide semiconductor region serves as a protective layer for the first oxide semiconductor region; thus, change in composition or deterioration in film quality of the first oxide semiconductor region can be prevented, and electrical characteristics of the thin film transistor can be stabilized.
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Citations
29 Claims
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1. A semiconductor device comprising:
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a gate electrode over a substrate; a gate insulating layer over the gate electrode; a source electrode and a drain electrode over the gate insulating layer; a first oxide semiconductor region over the source electrode and the drain electrode; and a second oxide semiconductor region over the first oxide semiconductor region, wherein part of the first oxide semiconductor region is in contact with the gate insulating layer and side surface portions of the source electrode and the drain electrode, wherein an electrical conductivity of the second oxide semiconductor region is lower than an electrical conductivity of the first oxide semiconductor region, and wherein the first oxide semiconductor region is electrically connected with the source electrode and the drain electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A semiconductor device comprising:
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a gate electrode over a substrate; a gate insulating layer over the gate electrode; a source electrode and a drain electrode over the gate insulating layer; a buffer layer having an n-type conductivity over the source electrode and the drain electrode; a first oxide semiconductor region over the buffer layer; and a second oxide semiconductor region over the first oxide semiconductor region, wherein part of the first oxide semiconductor region is in contact with the gate insulating layer and side surface portions of the source electrode and the drain electrode, wherein a carrier concentration of the buffer layer is higher than a carrier concentration of the first oxide semiconductor region, wherein an electrical conductivity of the second oxide semiconductor region is lower than an electrical conductivity of the first oxide semiconductor region, wherein an electrical conductivity of the buffer layer is higher than the electrical conductivity of the first oxide semiconductor region and the electrical conductivity of the second oxide semiconductor region, and wherein the first oxide semiconductor region is electrically connected with top surfaces of the source electrode and the drain electrode through the buffer layer. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A semiconductor device comprising:
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a gate electrode over a substrate; a gate insulating layer over the gate electrode; a source electrode and a drain electrode over the gate insulating layer; an oxide semiconductor layer over the source electrode and the drain electrode; and an insulating layer interposed between part of the oxide semiconductor layer and side surface portions of the source electrode and the drain electrode, wherein the oxide semiconductor layer contains at least one of indium, gallium, zinc, and tin, and wherein the oxide semiconductor layer is electrically connected with the source electrode and the drain electrode. - View Dependent Claims (25)
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26. A method for manufacturing a semiconductor device comprising:
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forming a gate electrode over a substrate; forming a gate insulating layer over the gate electrode; forming a conductive film over the gate insulating layer; etching the conductive film to form a source electrode and a drain electrode; forming a first oxide semiconductor film over the gate insulating layer, the source electrode and the drain electrode by a sputtering method; forming a second oxide semiconductor film over the first oxide semiconductor film by a sputtering method; and etching the first oxide semiconductor film and the second oxide semiconductor film to form a first oxide semiconductor region and a second oxide semiconductor region, wherein the first oxide semiconductor region is provided so that part of the first oxide semiconductor region is in contact with the gate insulating layer and side surface portions of the source electrode and the drain electrode, and wherein a proportion of a flow rate of an oxygen gas in a film-forming gas for forming the second oxide semiconductor film is made higher than a proportion of a flow rate of an oxygen gas in a film-forming gas for forming the first oxide semiconductor film. - View Dependent Claims (27, 28, 29)
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Specification