Effect of lower VDS on MOSFET Crss ( Reverse Transfer Capacitance )?
What is the change in Crss with VDS variation from zero to 1V?


Well, just think about the problem when VDS is 0 volts - VDS is on the cusp of becoming negative and, any signal applied to measure capacitance, is going to cause that to happen every half cycle. This makes the capacitance measurement problematic. 

So, the capacitance does increase more as you approach 0 V from a positive VDS but, when you pass through 0 V to a negative VDS, the capacitance begins to fall again (until you start to hit problems with the parasitic diode inside the MOSFET).

It's the same documentation problem with many Varactor (varicap) diodes except that a few suppliers do show the bias voltage below 1 volt as per the BB212: -



Picture acquired from this website.

Because the performance of a varactor is all about change in capacitance versus applied voltage, some manufaturers will provide this sort of information because it is somewhat fundamental to the main feature of the device. However, for MOSFETs, change in capacitance versus VDS is very much a secondary consideration in most applications so the manufacturer won't necessarily go over-board in covering operation below 1 volt.

This stack exchange page shows the BB109 varicap - the control voltage versus capacitance graph goes as low as 0.3 volts and, that's about as good as it gets for devices whose main function is acting as a voltage controlled variable capacitor. Having said that the MV2109 characteristic does go as low as 0.1 volts.

So, it's really all about the MOSFET supplier documenting most characteristics as reasonably as possible for the majority of likely applications.


  What is the change in Crss with VDS variation from zero to 1V?


I'm going to take an informed guess that there is a good work around if you could explain your application a bit more.