Demos transistors with sti and compensated well in drain

Abstract

A drain extended MOS (DEMOS) transistor with an element of field oxide separating the drain contact from the gate, and a compensation region of opposite polarity in the drain under the gate, is disclosed. The inventive DEMOS may be fabricated in a CMOS IC without adding any process steps. Both n-channel and p-channel versions may be fabricated in CMOS ICs with an n-type buried layer. Furthermore, the inventive transistor may be fabricated in an IC built in an SOI wafer. The width of the compensation region may be varied across multiple instances of the inventive DEMOS transistor to provide a capability for handling multiple signals with different voltage levels in the same IC without adding fabrication steps. The compensation region may be biased by a control voltage to modulate the depletion of the drain extension and provide a capability for handling multiple signal voltage levels in a single transistor.