A semiconductor device and a method of fabricating the semiconductor device are disclosed. The method includes forming nanostructured channel regions on a fin or sheet base, forming gate openings surrounding the nanostructured channel regions, forming oxide layers on exposed surfaces of the nanostructured channel regions and the fin or sheet base in the gate openings, performing a first doping process on the oxide layers to form doped oxide layers, depositing a first dielectric layer on the doped oxide layers, performing a second doping process on the first dielectric layer to form a doped dielectric layer, and depositing a conductive layer on the doped dielectric layer.