A 0.7-μm-gate-length metal-insulator-semiconductor field effect transistor (MISFET) was fabricated on a hydrogen-terminated diamond surface conductive layer. The maximum transconductance of 100 mS/mm was obtained by DC measurement. The cut-off frequency of 11 GHz and the maximum frequency of oscillation of 18 GHz were achieved for the fabricated MISFET biased at VGS=0 V and VDS= -12 V. These are the highest values for diamond MISFETs ever reported. In the MISFET, high-frequency small-signal equivalent circuit analysis is carried out at VGS=O V and VDS= -3, -5, -8, -10 and -12 V. The analysis indicates that the reduction of parasitic resistance between the source and gate is necessary for realizing higher output power.
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