I noticed a question regarding mosfet polarity asked here and wondered whether a four terminal mosfet would behave the same way under reversed polarity. Since the four terminal mosfet has no internal diode (I think), I do not see how there could be a distinction between source and drain. Is this true?
It would be possible to construct a four-terminal MOSFET that was symmetrical, with source and drain indeed being interchangeable. On the other hand, even with a four-terminal device, a non-symmetrical shape may allow performance in one direction to be improved beyond what would be possible with a symmetrical device. A MOSFET integrated onto a chip will often have a gate which is confined to a single plane above the active channel, but power MOSFETs have much more complicated three-dimensional structures which generally favor non-symmetrical designs.