Advanced transistors (FinFET and GAA)

What is an advantage of fully depleted SOI (FD-SOI) transistors?

  1. AThe silicon layer can be thick and heavily doped
  2. BNo gate electrode is needed
  3. CThe channel can be lightly doped, threshold voltage variation is reduced, and the threshold is easy to adjust with body bias
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Answer: C. The channel can be lightly doped, threshold voltage variation is reduced, and the threshold is easy to adjust with body bias

In FD-SOI, the entire extremely thin silicon layer is depleted, so short-channel effects are suppressed without heavy channel doping. Threshold voltage variation due to dopant fluctuation is small, and the threshold can be adjusted by applying voltage from the substrate side through the thin buried oxide.

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More Advanced transistors (FinFET and GAA) questions

  1. In very small transistors, what is the phenomenon called in which the threshold voltage varies because of statistical variation in the number and positions of dopant atoms in the channel?
  2. Compared with FinFETs, what is a design advantage of nanosheet GAA transistors?
  3. Which technique, used to make the thin fins of FinFETs, uses sidewall spacers to create patterns finer than the lithography limit?
  4. In manufacturing nanosheet GAA transistors, why is only the SiGe selectively removed from stacked alternating Si and SiGe layers?
  5. What is the cause of self-heating, which tends to be a problem in FinFETs and SOI transistors?