A semiconductor device and a method of manufacturing are provided. A dielectric layer is formed over a substrate, and a first silicon-containing layer, undoped, is formed over the dielectric layer. Atomic-layer doping is used to dope the undoped silicon-containing layer. A second silicon-containing layer is formed over first silicon-containing layer. The process may be expanded to include forming a PMOS and NMOS device on the same wafer. For example, the first silicon-containing layer may be thinned in the PMOS region prior to the atomic-layer doping. In the NMOS region, the doped portion of the first silicon-containing layer is removed such that the remaining portion of the first silicon-containing layer in the NMOS is undoped. Thereafter, another atomic-layer doping process may be used to dope the first silicon-containing layer in the NMOS region to a different conductivity type. A third silicon-containing layer may be formed doped to the respective conductivity type.