Advanced transistors (FinFET and GAA)

In FinFETs built on bulk substrates, what is the purpose of a heavily doped layer at the base of the fin (the part the gate controls poorly)?

  1. ATo suppress punch-through leakage flowing through the lower part of the fin
  2. BTo lower the gate resistance
  3. CTo make the fin taller
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Answer: A. To suppress punch-through leakage flowing through the lower part of the fin

In a bulk FinFET, the lower part of the fin is not surrounded by the gate, so current leaks easily between source and drain there. A heavily doped layer of the opposite type to the channel near the fin base (a punch-through stopper) suppresses leakage through this path. With an SOI substrate, isolation is provided by the buried insulator instead.

  • A. Correct. It suppresses leakage under the fin.
  • B. It is unrelated to the gate electrode's resistance.
  • C. It is not a layer for changing fin height.
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More Advanced transistors (FinFET and GAA) questions

  1. Which correctly describes the "scale length (natural length) λ" used to estimate the severity of short-channel effects?
  2. What is an effect of quantum confinement when fins or nanosheets are thinned to a few nanometers?
  3. In a FinFET made in the usual orientation on a (100) wafer, the fin sidewalls that form the channel are mainly (110) planes. What is the effect on mobility?
  4. Which correctly describes the structure of a FinFET?
  5. Which correctly describes a GAA (gate-all-around) transistor?