Device providing multiple threshold voltages and methods of making the same

Abstract

A semiconductor structure includes a substrate, a first transistor disposed over the substrate and including a first channel, a first interfacial layer over the first channel, a first gate dielectric layer over the first interfacial layer, and a first gate electrode layer over the first gate dielectric layer, and a second transistor disposed over the substrate and including a second channel, a second interfacial layer over the second channel, a second gate dielectric layer over the second interfacial layer, and a second gate electrode layer over the second gate dielectric layer. The first gate dielectric layer includes a first dipole material composition having a first maximum concentration at a half-thickness line of the first gate dielectric layer. The second gate dielectric layer includes a second dipole material composition having a second maximum concentration at a half-thickness line of the second gate dielectric layer and greater than the first maximum concentration.