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Abstract

To obtain a semiconductor device containing TFTs of different, suitable properties as display pixel TFTs and high-voltage, driver-circuit TFTs, the semiconductor device of the present invention includes: first and second islands-shaped polycrystalline silicon (p-Si) layers provided above an insulating substrate and having relatively large grain sizes; a third islands-shaped p-Si layer having relatively small grain sizes; a first gate insulating film provided on the first p-Si layer and having a first thickness; second and third gate insulating films provided on the second and third p-Si layers having second and third thicknesses which are not less than the first thickness; gate electrodes provided on the gate insulating films; n-type high-concentration source/drain regions formed by adding an n-type impurity to a high concentration outside channel regions; and second and third n-type low-concentration-source/drain regions provided between the channel regions and the n-type high-concentration source/drain regions of the second and third p-Si layers. The third n-type low-concentration source/drain regions have a higher impurity dose than the second n-type low-concentration source/drain regions.

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First Claim