Insulator substrate for a light valve device having an electrostatic protection region

摘要

A semiconductor on insulator substrate has improved electrostatic performance without sacrificing the performance of commonly integrated high-speed integrated circuitry. The semiconductor on insulator substrate includes a single crystal semiconductor thin film having an integrated circuit region and an electrostatic protection region. The thickness of the single crystal semiconductor thin film is greater in the electrostatic protection region than in the integrated circuit region to thereby allow high-speed operation of devices formed in the integrated circuit region. Such a substrate has particular application as a driving substrate for a light valve. In such a device, the integrated circuit region includes thin film switching transistors for selectively applying a voltage to the liquid crystal layer and thin film driving transistors for driving the thin film switching transistors. The electrostatic protection region includes an electrostatic protection device electrically connected to the integrated circuit region, and the electrostatic protection device is effective to protect the driving transistors from exposure to an excess of electrostatic charge.