hello,
as every one said it depends on the fab, but 350nA looks really lesser than the published one. Please refer the following jssc pap, they have reported few numbers on leakage, for 900um^2 hey have 1mA leakage current.
http://www2.ee.ntu.edu.tw/~ecl/Professor/A%20Leakage-Current-Recycling%20Phase-L...Try to read some more from the same authors you will find few more interesting leakage numbers.
try to simulate in the following manner.
By applying 1V ac voltage source at the gate of cap and measure current through gate.
Thanks,
Raj.