CMOS Compatible Sub-Threshold Silicon MESFETSs and Methods of Forming the Same

Metal Semiconductor Field Effect Transistors (MESFETs) have a number of advantages over MOSFETs. These advatages include lower noise and higher operating frequency. When a MESFET is configured to operate as a Schottky Junction Transistor (eg for micropower circuit applications) it also gas the advantage of increased operating freqquency at a given drain current density. The majority of MESFETs are designed using GaAs based materials and the resulting circuits are more expensive to manufacture than is the case for silicon CMOS. This invention describes how silicon MESFETs can be fabricated using commercially available silicon-on-insulator (SOI) CMOS processes. No change is required to the CMOS process flow and this allows complementary MESFETS and MOSFETs to be integrated together on the same circuit without increasing the cost.