Process to fabricate a metal high-K transistor having first and second silicon sidewalls for reduced parasitic capacitance

摘要

A method forms a metal high dielectric constant (MHK) transistor and includes: providing a MHK stack disposed on a substrate, the MHK stack including a first layer of high dielectric constant material, a second overlying layer, and a third overlying layer; selectively removing only the second and third layers, without removing the first layer, to form an upstanding portion of a MHK gate structure; forming a first sidewall layer on sidewalls of the upstanding portion of the MHK gate structure; forming a second sidewall layer on sidewalls of the first sidewall layer; removing a portion of the first layer to form exposed surfaces; forming an offset spacer layer over the second sidewall layer and over the first layer, and forming in the substrate extensions that underlie the first and second sidewall layers and that extend under a portion but not all of the upstanding portion of the MHK gate structure.