[Radio Wrangler]

Different, but you have to work at it to see the difference. A little battery powered hand-held tester won't show it.

The zener looks like a normal diode when biased the opposite way, but then so do most MOSFETs across d-s. So nothing unusual. To find the difference you have to take d-s voltage high enough in the normal direction for the zener clamp to act. A normal MOSFET would just let Vds gohigher until damage happened.

MOSFETs made the usual way have an unavoidable diode across drain-source which will turn on if the drain-source pair get reverse biased. In things like SMPS and class D transmitters, great care has to be taken to make sure this diode never gets turned on, because it's rather slow and won't turn off at the speed of the transistor itself... this leads to pops, bangs and smoke. In the case of these transistors, the implicit diode is made to have avalanche characteristics. (Zener is a misnomer, real zener effect diodes are all low voltage)

David