The reverse gate leakage mechanism of W-gate and TiN-gate AlGaN/GaN HEMTs with N2 plasma surface treatment is investigated by using current-voltage (I-V), capacitance-voltage (C-V) characteristics and theoretical calculation analysis. It is found that the main reverse gate leakage mechanism of both devices is the trap-assisted tunneling (TAT) mechanism at the entire reverse bias region (-30V - 0V). To the best of our knowledge, this is the first time that the analysis of the reverse gate leakage mechanism of W-gate AlGaN/GaN HEMTs has been studied. It is also found that the reverse gate leakage current of the W-gate AlGaN/GaN HEMTs is smaller than that of the TiN gate at high reverse gate bias voltage. Further, the activation energies of the extracted W-gate and TiN-gate AlGaN/GaN HEMTs are 0.0551eV-0.127eV and 0.112eV-0.201eV, respectively.

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