In this article, we investigate the effects of gate and drain field plates and isosceles trapezoidal-shaped multi-finger structures on the characteristics of high current p-GaN-gated high-electron-mobility transistors (HEMTs). By optimizing the lengths of gate and drain field plates, the p-GaN-gated HEMTs with 200 μm have a breakdown voltage of 1893 V, a specific on-resistance of 7.0 mΩ-cm2, and a Baliga figure of merit (BFOM) value of 511 MW cm−2. Using the optimized isosceles trapezoidal-shaped multi-finger metallization on the source and drain, the p-GaN-gated HEMT with a 100 mm gate width can reach a current of 2.3 A. Combining all the optimum parameters of field plates and isosceles trapezoidal-shaped multi-finger, the fabricated 600 mm p-GaN-gated HEMT exhibits an output current of 18 A, an on-resistance of 0.7 Ω, and a breakdown voltage of 1020 V. Furthermore, the device also exhibits good thermal stability at high temperatures. These results demonstrate the potential and advantages of p-GaN-gated HEMT for power applications.