Semiconductor device having dynamic threshold transistors and element isolation region and fabrication method thereof

摘要

A semiconductor device with dynamic threshold transistors includes a complex element isolation region composed of a shallow element isolation region made of shallow trench isolation and deep element isolation regions provided on both sides of the shallow element isolation region. Since the shallow element isolation region is made of the shallow trench isolation, Bird's beak in the shallow element isolation region is small. This prevents off leakage failure due to stress caused by the bird's beak. The deep element isolation region has an approximately constant width which allows the complex element isolation region to be wide.