Method for manufacturing gate stack structure in insta-metal-oxide-semiconductor field-effect-transistor

Abstract

A method for manufacturing a metal-oxide-semiconductor (MOS) gate stack structure in an insta-MOS field-effect-transistor (i-MOSFET) includes the following steps of: forming a silicon nitride layer over a silicon substrate; forming a nanopillar structure including a silicon-germanium alloy layer in contact with the silicon nitride layer; and performing a thermal oxidation process on the nanopillar structure to cause germanium atoms in the silicon-germanium alloy layer to penetrate the underneath silicon nitride layer to form a silicon-germanium shell layer in contact with the silicon substrate and a germanium nanosphere located over the silicon germanium shell layer, and to form a separating layer between the silicon-germanium shell layer and the germanium nanosphere by oxidizing silicon atoms from the silicon nitride layer or the silicon substrate, thereby forming a germanium/silicon dioxide/silicon-germanium i-MOS gate stack structure capable of solving interfacial issues between silicon and germanium and between germanium and the gate dielectric.