As Vg falls, both Vd and Vs fall. Vds is zero for the first 4ns, suggesting the FET is still conducting. I'm guessing that the voltage loss is caused by the gate charge transfer.
As Vgs reaches about -0.6V there is a change in its
Unfortunately, Vd fails to remain at 2.0V; this is why the FDV301 is not suitable in this circuit. Seemingly paradoxically Vd rises about 0.3V, then resumes its fall until goes negative, both in respect to ground and to Vs. The disconnect between Vd and Vs reinforces my thought that the FET is off from the point these signals diverge.
What's causing the drain to fall? Why does Vds go negative? I'm really not sure. If anyone out there has a suggestion, feel free to make it!