Ion Implantation

Ion implantation is also used to form a transistor's well regions, the larger, deeper doped regions (N-well for PMOS, P-well for NMOS) that establish the base doping environment each transistor type is built within, distinct from the much shallower source/drain or threshold-adjust implants performed later in the process flow. Well implants typically use higher implant energy than source/drain implants specifically because they need to reach much greater depth, reflecting the well's role as a deep structural doping region rather than a shallow, surface-level junction.