Ion implantation continues being the dominant technique to introduce dopants in Si devices. With the device feature size in the nanometer scale, the accurate and detailed description of as-implanted dopant and damage profiles is becoming key as advanced annealing techniques are almost diffusionless. The demanding requirements for ultrashallow junction formation are stimulating the development of improved and detailed models for molecular implants and for the kinetics of amorphous damage, Additional challenges arise in the doping of advanced architectures, such as fin field effect transistors, because the introduction of highly tilted ions is quite inefficient and, in addition, the regrowth of amorphous regions in narrow structures is hampered by the slow regrowth at free interfaces and {111} planes. Atomistic simulations play a relevant role to provide the understanding for the development of simplified physically based models computationally more efficient. (C) 2010 American Vacuum Society [DOI: 10.1116/1.3231481]