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CMOS Fabrication Technology

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Hi

In the below shown figures, First one is Top view and the second one is cross-sectional view.

In the cross-sectional view(second fig): for P-mos transistor -> in n-well region there is P+ for both source and drain, but near the drain region there is also n-well contact included. What is this? why is this included during CMOS Fabrication Technology> Is it purposely included? Is is acting like resistor?

Also in the Top View(first figure) it is showing, in n-well the pmos is connected to VDD. Is this right?
 

its a body/substrate contact...my suggestion read a good book on MOS device and then fabrication...refer book on semiconductor devices by ben streetman...
 

i m having one more doubt in CMOS.
why pmos is fabricated on N-well. But why on Nmos?
Nmos is not in well in a CMOS? any specfic reson.
thanks in advance for good replies.
dont reply refer this books to me
 

This is called well ties, the purpose is to tie N well to most positive supply (VDD), thus prevent substrate and N well from being forward biased (latch-up).

Why PMOS on N well? If not, how do you turn it on? You need to read some basic book on CMOS technology.
 

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