That fet is specified for a max of 250uA leakage at 150*C, 60v D-S. If you are getting 200mA of leakage, either your MOSFET is broken or the circuit is incorrect. It is n- channel, so you are using it as a low-side switch with a grounded source, right? Note the very low Vgs max of 10v, these would be easy to fry with ESD or a simple mistake putting together the circuit. Measure the resistance between gate and source with a meter. If it is not infinite, the MOSFET is bad. If you are at a university studying EE, I am sure they have some logic-level fets you could replace it with. It is most likely that you have the fet connected incorrectly, however(source not grounded). Also make sure the 9v battery and the MCU share a common ground.
Good luck!