Patent ID: 8786030

Claim:
A quarter-gap n-type field effect transistor (NFET) formed by gate-last fabrication, the quarter-gap NFET comprising: a gate stack formed on a silicon substrate, the gate stack comprising: a high-k dielectric layer located on the silicon substrate; and a gate metal layer located over the high-k dielectric layer, the gate metal layer comprising titanium nitride and having the gate metal layer a thickness from about 30 angstroms to about 100 angstroms; a threshold voltage tuning layer located between the high-k dielectric layer and the gate metal layer, wherein the threshold voltage tuning layer comprises a layer of lanthanum having a thickness from about 4 angstroms to 100 angstroms wherein the thickness of the threshold voltage tuning layer is based on a thickness of the gate metal layer; and a metal contact formed over the gate stack, wherein an effective work-function of the quarter-gap NFET is about 4.325 electron-volts.