i found the problem - you have assigned bulk conductivity to the silicon and silicon dioxide. remove this and the simulation works. i have not been able to use conductivity in a dielectric and wave ports together. in those cases, i use lumped ports and terminal mode solution.
in general, wave ports should be much larger than the conductor they are illuminating. they should cover the conductor and a large portion of the dielectric. otherwise the results will not be accurate. you can see this in the HFSS manual example 6.5.