Semiconductor device capable of threshold voltage adjustment by applying an external voltage

摘要

A semiconductor device has a silicon substrate, in which an active region is formed between two device isolation films and a gate is formed on the surface of the active region. The silicon substrate has a laterally etched portion in the active region below the surface of the active region on the side near the device isolation film. An insulating film is formed on the laterally etched portion of the silicon substrate. A conductive electrode is formed on the insulating film, through which an external voltage is applied to adjust a threshold voltage. The device isolation film is formed on the conductive electrode. None or some pockets of vacant cavity is present between the device isolation film and the conductive electrode.