Can I implement MOSCAP in an FPGA? I mean can I connect drain and source of a transistor to gnd and gate to another node? It can be another device other than FPGA. Thank you.
No, you don't have control over connections at the transistor level when using an FPGA. You need to draw your own layout for the MOSCAP and build it as a full-custom IC. I hope you have lots of money for this.