There should be no problem.

Deposit your insulating ZnO on silicon wafer, and then fabricate your sourcs and drain electrodes at the distance of 50 microns., and finally back metallize you silicon wafer.

just ensure that you have a clean interface at the ZnO-silicon interface. Just look into the design MOS field effect transistors, you will find different insulators being used. and this is the most simplest structure of all. Well you need to do a lot literature survey, and I am sure you will find many papers.

K. Sreenivas