We fabricated diamond MISFETs on polycrystalline films using alumina gate insulator. A hole accumulation layer has been utilized as hole current channel. The hydrogen-termination was achieved by remote hydrogen plasma. The sheet resistance strongly depends on the substrate temperature during hydrogen-termination process. The polycrystalline diamond MISFETs showed high drain current density of -650 mA/mm and cut-off frequency of 42 GHz. These values are higher than those of single crystal diamond FETs ever reported.