For the first time, the channel discrete dopant profiling (DDP) of small devices are demonstrated experimentally based on a quasi-2D Vth model. The discrete -dopant distribution along the channel direction can be determined. Boron cluster in nMOSFETs was observed, resulting in a larger V th variation, in comparison to that of pMOSFETs. Moreover, experiments have been extended to the advanced strain-CMOS devices. For the SiC S/D nMOSFET, the carbon out-diffusion has been identified; for SiGe S/D pMOSFET, Ge out-diffusion has also been observed. This approach provides a direct-observation of the random dopant fluctuation (RDF) and is useful for studying the Vth variability of future generation CMOS devices.