Hi, I would like to ask about the behavior of a MOSFET as a capacitor, particularly at the onset of inversion/weak inversion - see Fig 2.6(c)
- At this stage in Fig 2.6(c), there is positive charge at the gate metal/poly contact, then an insulator oxide and then negative ions (positive holes have been repelled) - this is the Cox capacitor in the schematic overlaying.
- My confusion is regarding the Cdep - depletion region capacitor. What are the two 'plates' or regions of charge accumulation that form the Cdep capacacitor? I assume one is the negative ions (sharing a plate with Cox) and the other is the repelled positive holes. But then, if you see my drawn schematic, that doesn't make sense, since the + charges are on top and negative ions should be on top?
Can someone explain to me how Razavi is extrapolating from the device physics that there is a Cdep capacitance? What are the two regions of charge that form Cdep? Is one 'plate' shared with Cox?