Hi everyone, I have a question about the importance of symmetry when laying out a field-effect transistor (FET) in Glayout. Specifically, can I swap the source and drain terminals during layout? My understanding is that the current flow direction determines which terminal acts as the source and which acts as the drain. Is this correct? If so, does it matter how the FET is physically oriented in the layout as long as the biasing is set appropriately?

If the objective is to match the characteristics of two transistors, their orientation and direction of current flow must be the same. The s/d implants on each side of the transistor are not perfectly symmetric since the dopants are shot into the substrate at an angle. We should get into these issues in a meetup where we talk about best layout practices.