Can we neglect body effect in small channel length(length is less than 30 nm) surrounding gate MOSFET device or is it still a dominating factor while calculating threshold voltage?
Dear Amit Das ,
Depending on the technological parameters and partly on the dimensions of the MOSFET, body effect may be larger or smaller, but unfortunately you cannot expect it to be negligible.
You can avoid body effect on a MOSFET when you use it with its source-body terminals shorted (This may be restricted, however, by your circuit topology and the facilities of the technology).
In a single-well CMOS technology only one type of MOSFET can benefit from S-B shorting regardless of the circuit topology. If we assume n-well CMOS, a pMOS transistor can own its independent well (pMOS body), so S-B shorting can be possible for any pMOST (if you provide it with its own n-well). In n-well CMOS, S-B shorting for an nMOS transistor can be possible only if its source terminal is connected to the lowest potential (ground or -Vss) to which the p-substrate (common body of all nMOS transistors) is connected.
In a twin-well CMOS technology, both n-wells and p-wells are available, which make S-B shorting for both nMOS and pMOS transistors possible (if they have their own wells). So, a twin-well CMOS technology permits you avoid body effect for any transistor but this in turn increases the area occupied by the circuit, and may also degrade the speed (due to large parasitic capacitances coming from individual wells).
Best regards...
I am sorry dear Amit Das ,
The comments I wrote above are valid for classical MOSFETs and many other types.
I noticed now, however, that you asked for GAA MOSFET, some types of which show good body-effect immunity.
I regret I did not get your question completely in the first position. It's my fault.
Nevertheless, with your permission, I want to keep the above answer, because it's a satisfactory explanation for many types of MOSFETs.
I am sorry if I have misled you.
On the other hand, I don't feel self-confident to give you a satisfying answer specific to GAA MOSFET, because I don't have experience about it.
I hope other researchers can give satisfying answers.
Best regards...
Dear Ali Zeki sir,
Your answer is quite satisfactory and I found your answer quite satisfactory. I think you are right sir that in short channel MOSFET, body effect might be very less and the second explanation that gate all around MOSFET have better body-effect immunity is quite satisfying. Thank you so much for your valuable response.
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