HEMT having a drain field plate is provided. The drain field plate is formed in the area between the gate and drain of a HEMT. The drain field plate includes a metal pad that has a larger projection area than the drain pad. The drain field plate and semiconductor layer disposed beneath the drain field plate form a metal-semiconductor (M-S) Schottky structure. The capacitance of the M-S Schottky structure generates capacitance in the semiconductor area, which increases the breakdown voltage of the transistor components of the HEMT. A portion of the substrate under the active area may be removed to thereby increase the heat conductivity and reduce the junction temperature of the transistor components of the HEMT.