I have designed a capacitor using Tanner L-Edit v13.
There is only one type of poly in the library. I designed it using poly and poly_cap.
But after the extraction, i got zero capacitance. How to get the capacitance value?
here is the extraction result
This doesn't depend on your design tool (Tanner, which I don't have access to, anyway), but on your PDK (physical design kit). You should tell which one you're using (from which foundry), and for which process size.
In CMOS there are always MOSCAPs (poly|gate_oxide|bulk) and MOMCAPs (metal|thick_ox|metal) available, sometimes you can get a MIMCAP (metal|thin_insulator|metal) option.