To provide an electrooptic device which can reliably suppress a substrate floating effect, such as a parasitic bipolar phenomenon, in an SOI-MIS transistor, and which has superior electrical characteristics. An electrooptic device (liquid crystal light valve) of the present invention uses, as one substrate, a composite substrate including a quartz substrate (main substrate 10A) having a first coefficient of thermal expansion, an insulating layer (insulating underlayer 12) formed on the quartz substrate, and a single-crystal silicon layer (semiconductor layer 1a) formed on the insulating layer and having a second coefficient of thermal expansion. A TFT 30 that uses the single-crystal silicon layer as a channel region 1a' is formed on the insulating layer, and at least one line defect D exists in the single-crystal silicon layer that forms the channel region 1a'.