Patent ID: 7245330

Claim:
An electrooptic device having a composite substrate, comprising: a support substrate having a first coefficient of thermal expansion; an insulating layer formed on said support substrate; a single-crystal semiconductor layer formed on said insulating layer and having a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion, the single-crystal semiconductor layer including a channel region, heavily-doped regions on either side of the channel region, and a lightly-doped region between each of the heavily-doped regions and the channel region; and a thin-film transistor using said single-crystal semiconductor layer as a channel region that is formed on said insulating layer, and said single-crystal semiconductor layer that forms said channel region including at least one line defect caused by warping when the two different thermal expansion coefficient layers are attached together, the line defect extending across the channel region, the lightly-doped regions, and the heavily-doped regions, the line defect forming a recombination center of excess carriers produced by optical excitation when light enters the lightly-doped regions.