| CPC H01L 29/7869 (2013.01) [G09G 3/3266 (2013.01); H01L 27/1225 (2013.01); H01L 29/24 (2013.01); H01L 29/41733 (2013.01); H01L 29/66969 (2013.01); H01L 29/78696 (2013.01); G09G 3/3291 (2013.01); G09G 2300/0426 (2013.01); G09G 2300/0819 (2013.01); G09G 2300/0842 (2013.01); G09G 2310/0245 (2013.01); G09G 2310/08 (2013.01)] | 20 Claims |

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1. A method of manufacturing a thin film transistor comprising:
forming a gate electrode on a substrate;
depositing a gate dielectric layer on the gate electrode;
forming a first oxide semiconductor layer including indium (In), gallium (Ga), zinc (Zn), tin (Sn), and oxygen (O); and
forming a second oxide semiconductor layer including indium (In), gallium (Ga), zinc (Zn), and oxygen (O),
wherein a content ratio Ga/Zn of the second oxide semiconductor layer is higher than a content ratio Ga/Zn of the first oxide semiconductor layer,
wherein in the first oxide semiconductor layer, a content ratio of In to Sn satisfies 2.5≤In/Sn≤5, a content ratio of Ga to Sn satisfies 1≤Ga/Sn≤2, and a content ratio of Zn to Sn satisfies 2.5≤Zn/Sn≤5, and
wherein the content ratio of Ga/Zn of the first oxide semiconductor layer is less than 1 and the content ratio of Ga/Zn of the second oxide semiconductor layer is less than 1.
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