This paper analyzes the drain breakdown voltage of multigate MOSFETs and the influence of parameters such as doping concentration, fin width, and gate length. The good electrostatic control of the active area by the multigate structure improves the drain breakdown voltage, which increases as the fin width is decreased. Increasing the channel doping concentration improves the drain breakdown voltage as well.
Lee, C.-W., Afzalian, A., Yan, R., Dehdasti Akhavan, N., Xiong, W., & Colinge, J.-P. (2008). Drain breakdown Voltage in MuGFETs: Influence of Physical Parameters. IEEE Transactions on Electron Devices, 55(12), 3503-3506. https://doi.org/10.1109/TED.2008.2006546 (Original work published 2008)