Sub-threshold Slope Factor

Thread Starter


Joined Aug 14, 2017
Sub-threshold slope factor is given by :
Cd = depletion capacitance
Cox= oxide capacitance

How to calculate the Sub-threshold slope factor for different technology nodes? I m able to substitute for Cox but i don't know how to calculate Cd...i m using the basic inverter circuit


Joined May 15, 2009
Tricky one this. Not quite sure what you are trying to achieve but the depletion capacitance is determined from the doping level of the transistor(s) you are using. To know that you will need to know the physical construction of the transistor.

The depletion capacitance (are we talking MOSFET?) can be calculated assuming a doping level and integrating it for a given voltage. It's not particularly difficult, but does need some device physics assumptions and info about the device technology. You can check whether the threshold voltage is right for the expected technology but there are other factors (work function) to be considered too.

You might be able to measure it but that will required specialised equipment able to measure very low capacitances (unless you are considering large transistors).