This question is a bit premature as I don't have any intention to create any silicon chips right away. But I have an idea of an integrated circuit which depends on what I will be able to squeeze into one.
And the main thing I have doubts about is a HV capacitor. My simulation shows that I will need to have 350 (or 400 even better – 230 VAC + 10-15%) Volts with 100 pF capacitance.
Unfortunately I don't know which limitations are applied to capacitors integrated into silicon chips. Does anybody knows?
Best Answer
On chip capacitors take a lot of chip area making them expensive. I'm currently working on a process where they can make metal capacitors of 2 femto Farad per square micrometer. So a 100 pF capacitor would have take up an area of 50000 sq um so 500 x 100 um.
But these capacitors can handle only up to 10 Volts or so, nowhere near your 350-400 V requirement.
Maybe there are specialist high-voltage processes in which high voltage capacitors can be made but I doubt that. Edit: Doubt taken away, there are, see comments.
For 350-400 V you need a strong and/or large dielectric which can withstand the fieldstrength. This is not easy to fit in a small size (like an IC).