MOS

Question 1

Estrutura nMOSFET

Answer 1

– The gate electrode is placed on top of a very thin insulating layer.
– There is a pair of small n-type regions just under the drain & source electrodes.
– A positive voltage applied to gate will push away the ‘holes’ inside the p-type substrate and attracts the moveable electrons in the n-type regions under the source & drain electrodes (inversion region)
– The overlap between the gate and the source/drain region is required to ensure that the inversion layer forms a continuous conducting path between the source and drain region.
– Typically this overlap is made as small as possible in order to minimize its parasitic capacitance.

Question 2

D-MOSTFET and E_MOSFET

Answer 2

D-Mosfet: canal restringido pela tensão da gate
E-Mosfet: canal é criado pela tensão na Gate

Question 3

Mobilidade canal MOSFET

Answer 3

– Mobility depends on gate voltage – carriers in inversion channel are attracted to gate – increased surface scattering – reduced mobility

Question 4

Subthreshold regime

Answer 4

– For gate voltage less than the threshold – weak inversion
– Diffusion is dominant current mechanism (not drift)