Advanced transistors (FinFET and GAA)

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?

  1. ANeither electron nor hole mobility changes
  2. BCompared with the (100) plane, hole mobility tends to rise and electron mobility tends to fall
  3. CBoth electron and hole mobility increase greatly
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Answer: B. Compared with the (100) plane, hole mobility tends to rise and electron mobility tends to fall

Silicon mobility depends on the crystal plane and current direction: on (110) planes, hole mobility tends to be higher and electron mobility lower than on (100). Because most FinFET current flows along the sidewalls, the orientation favors pMOS and penalizes nMOS, and performance is tuned in combination with strain engineering and similar techniques.

  • A. Mobility does change with the crystal plane.
  • B. Correct. Holes tend to benefit and electrons to lose.
  • C. Electron mobility actually tends to drop on (110) planes.
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More Advanced transistors (FinFET and GAA) questions

  1. Which correctly describes the structure of a FinFET?
  2. Which correctly describes a GAA (gate-all-around) transistor?
  3. Which describes a short-channel effect in MOSFETs?
  4. What is the main reason for using high-k (high-dielectric-constant) materials for the gate insulator?
  5. What is the main purpose of applying strain (stress) to a transistor's channel?