P-channel MOSFET with heavily doped P-type poly-Si gate has a threshold voltage of -I. S Y with V sb = 0 V. When a 5 V reverse bias is applied to the substrate. the threshold voltage changes to 2.3 V.
(a) What is the dopant concentration in the substrate if the oxide thickness is 100 nm?
(b) What is the threshold voltage if Vsb is 2.5 V?