The cell size is required to increase for better convergence while execution?

[techenthusiast]

Dear experts,

Good morning, just to ask, normally: For this kind of structure (Long devices), The cell size is required to increase for better convergence while proper task execution? in conventional cases? if yes, how to do that for existing device structure/geometry. Thank you.
Note: I have enclosed the structure.

[Anders Blom]

Not really for better or faster convergence, but if the box is too small, there is some unphysical electrostatic interaction with the repeated copies. So the box in the direction you indicated needs to be large enough that this does not influence the results. With gates included as in your case, you can use a relatively small size box, but at the same time, unless the box is very, very large, it doesn't change the simulation time by much.