| CPC H01L 29/7869 (2013.01) [H01L 23/5226 (2013.01); H01L 23/544 (2013.01); H01L 29/78648 (2013.01); H01L 29/78696 (2013.01); H01L 2223/5446 (2013.01)] | 33 Claims |

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1. A semiconductor device comprising:
a transistor comprising:
a gate electrode;
a gate insulating film; and
an oxide semiconductor layer comprising indium, an element M, and zinc,
wherein the element M is one or more of Al, Ga, Y and Sn,
wherein the oxide semiconductor layer comprises a first region and a second region and a third region,
wherein an atomic ratio of In to the element M in the second region is greater than an atomic ratio of In to the element M in the first region,
wherein an atomic ratio of In to the element M in the third region is greater than the atomic ratio of In to the element M in the first region, and
wherein the second region and the third region are surrounded with the first region.
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