In virtuoso, there is select layer over active layer to identify the tpye of the active layer, along with related design rules (like select layers can not overlap).
My question is when we use n-well or p-well process, we need to moderate dope our substrate to create wells first, but why there is not a select layer to identify what kind of wells we want and not related design rules?
Actually the well layer is sufficiently larger to accomadate all implants.. and these wells(if twintub) are seperated enough by FOX layer and of course these wells must be seperated to avoid undesirable current injection.. These wells ofcourse fabricated on any substrate (n or p).
Precisely, they dont overlap..