Advanced transistors (FinFET and GAA)

How did the subthreshold swing (SS) generally change with the move from planar transistors to FinFETs?

  1. AIt fell below the theoretical limit of about 60 mV/dec
  2. BIt approached (decreased toward) the theoretical limit of about 60 mV/dec
  3. CIt increased, making the device harder to turn off
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Answer: B. It approached (decreased toward) the theoretical limit of about 60 mV/dec

Subthreshold swing is the gate voltage needed to change the drain current by one decade below threshold, with a theoretical limit of about 60 mV/dec at room temperature. In a FinFET the gate controls the channel from three sides, strengthening its control, so SS approaches the 60 mV/dec limit. However, conventional MOSFET physics cannot go below 60 mV/dec.

  • A. Conventional MOSFETs cannot go below 60 mV/dec because of the thermal limit.
  • B. Correct. Stronger gate control brings it closer to the limit.
  • C. SS improves (decreases) in FinFETs.
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More Advanced transistors (FinFET and GAA) questions

  1. As physical scaling becomes harder, what is the practice of considering design and process technology together to optimize area and performance called?
  2. In nanosheet GAA transistors now in production, how many nanosheets are typically stacked in one transistor?
  3. Which structure places nMOS and pMOS nanosheets close together on either side of a thin insulating wall to reduce cell area?
  4. What is the state called in which the channel is so short that carriers travel from source to drain almost without scattering?
  5. Which transistor has a source, channel and drain of the same conductivity type and doping, with no PN junctions?