Silicon-on-insulator gate-all-around mosfet fabrication methods

Abstract

A silicon-on-insulator (SOI) gate-all-around (GAA) metal-oxide-semiconductor field-effect transistor (MOSFET) includes a source, channel and drain surrounded by a top gate and a buried bottom gate, the latter of which also has application for other buried structures and is formed on a bottom gate dielectric which was formed on source, channel and drain semiconductor layer of an SOI wafer. After forming a planar bottom insulator layer on the bottom gate and bottom gate dielectric, the SOI wafer is flip-bonded onto an oxide layer of a bulk silicon wafer, thereby encapsulating the buried bottom gate electrode in insulating oxide, after which the SOI substrate and the etch-stop SOI oxide layer are removed to expose the SOI semiconductor layer which is processed to form the source, drain and channel in a mesa structure on which is deposited a top gate dielectric, a top gate, and top gate insulator as well as four conductors for connecting to the source, drain, top gate and bottom gate. The latter two electrodes can be independently controlled or commonly controlled for enhanced operation of GAA MOSFET having improved isolation and reduced parasitic capacitance due to the use of encapsulating insulation layers of the merged wafer consisting of the bonded SOI wafer and bulk silicon wafer.