Several questions about 2N7000 transistors

Then modern process parts must be tougher. It was a huge fiasco because the company blamed the parts as being defective and Vishay blamed ESD. It was ESD.
A second company I worked for had similar failures - about 10 days after a tech changed a board, the similar VN10K mosfets failed. Like clockwork. Something to do with ESD damage and ion migration that made it take a while to fail. I learned ESD does not always immediately kill a semiconductor, instead it can do damage and take time to fail.
No idea why some parts are more fragile - is it metal gate+glass verses polysilicon? Or the surrounding parts connected to the gate give coverage and extra protection.
So after many bad experiences, I am leery about using parts such as 2N7002/BS170 with no gate zener. They have no ESD rating at all- not sure if that means anything 30 years later.

OP could look at BSS138L which is logic-level, low threshold 1.5V - so it is suitable for 3.3V MCU's. Note a BSS138K even lower VGS(on) 1.2V and has a 2,000V ESD rating but the other parts do not.
 
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