When designing the PCB layout for a DC-DC boost converter, one does not place a ground plane under the inductor, to prevent induced ground currents. Also, for SMD MOSFETs, the drain (switch node) usually serves as a heat sink, so, since it should be small but sink a lot of heat, it makes sense to pour it on both sides, connecting them with vias. Which means no ground plane underneath the switch node (I'm using an IRFH5025, if you'd like to visualize what the package looks like).
However, I am not clear on whether it is beneficial to place the ground plane under the rest of the MOSFET, specifically the gate trace, sense resistor, and current sensing filter.
On one hand, this might limit magnetic interference from the inductor. On the other hand, it would increase MOSFET gate capacitance and provide another path for return current, right underneath the quite sensitive current sense trace.
Here's a picture with the area I'm considering marked in orange:
So, should I leave this area clear of the ground plane?