what does bulk really mean?

[cherishing]

1.for instance, if a nmos is located in the p-well, then the bulk of the nmos is located in the p-well, if a pmos is located in the n-well, then the bulk of the pmos is located in the n-well, if a resistor is located in the substrate, then the bulk of the resistor is located in the substrate?
2.can bulk be used for isolation?how?

thanks

 

[sunking]

it depond on your process.
1. for res, depond on you res kind. say pdiff will be nwell
2. the bulk is well in fact. so can be used for isolation

 

[ocarnu]

1. yes, everything is right. Pay atention, there are some triple well processes where you can put nmos in separate well.
2. I don't understand de question, the bulk is just a terminal, you cannot use it for isolation. BTW, what do you mean by isolation? However you can use the Nwell for noise isolation purposes (e.g. guard rings). It extracts the noise through the parasitic capacitance, is like a decoupling cap.