Patent ID: 8836018

Claim:
A method for fabricating a semiconductor integrated circuit (IC), the method comprising: receiving a semiconductor device precursor, the semiconductor device precursor including: a substrate; source/drain regions on the substrate; a dummy gate stack separating the source/drain regions on the substrate; and a doped region in the substrate and under the dummy gate stack; removing the dummy gate stack to form a gate trench; performing an ion-implantation (IMP) to the doped region in the substrate and exposed in the gate trench; recessing the doped region exposed in the gate trench to form a channel trench; forming a channel layer in the channel trench; and depositing a high-k (HK) dielectric layer and a metal gate (MG) over the channel layer, prior to depositing the channel layer, depositing a back-diffusion barrier layer on the channel trench, wherein the back-diffusion barrier layer is extended on a sidewall of the channel trench to a bottom of the channel trench.