MOSFET

What problem results from depletion of the polysilicon on the gate electrode side of a polysilicon gate?

  1. AThe gate resistance becomes zero
  2. BThe transistor emits light
  3. CIt is equivalent to a thicker effective gate insulator, so drive current decreases
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Answer: C. It is equivalent to a thicker effective gate insulator, so drive current decreases

Polysilicon is a semiconductor, so when a gate voltage is applied, a thin depletion layer also forms on the gate electrode side. This depletion layer acts as a series capacitance, making the effective gate insulator thicker and reducing drive current. The introduction of metal gates solved this problem.

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  1. What is the general effect of lowering a MOSFET's threshold voltage?
  2. How are the transistors connected in a CMOS two-input NAND gate?
  3. Which phenomenon increases off-state leakage because band-to-band tunneling current flows due to the strong field where the gate overlaps the drain?
  4. What circuit advantage results from almost no current flowing into the gate of a MOSFET?
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