Abstract: A HEMT device including a substrate structure, a channel layer, a barrier layer, a gate electrode, a drain electrode, a first source field plate, a second source field plate, and a dielectric structure is provided. The first source field plate extends from the second side of the gate electrode to the first side of the gate electrode. The second source field plate is located on the first side of the gate electrode and is located between the drain electrode and the first source field plate. There is a gap between the first source field plate and the second source field plate. The first source field plate has an end adjacent to the gap. The thickness of the dielectric structure located directly below the second source field plate is greater than the thickness of the dielectric structure located directly below the end of the first source field plate.

Abstract: A high electron mobility transistor device including a channel layer, a first barrier layer, and a P-type gallium nitride layer is provided. The first barrier layer is disposed on the channel layer. The P-type gallium nitride layer is disposed on the first barrier layer. The first thickness of the first barrier layer located directly under the P-type gallium nitride layer is greater than the second thickness of the first barrier layer located on two sides of the P-type gallium nitride layer.

Abstract: A high electron mobility transistor device including a channel layer, a first barrier layer, a gate structure, and a spacer is provided. The first barrier layer is disposed on the channel layer. The gate structure is disposed on the first barrier layer. The gate structure includes a first P-type gallium nitride layer, a second barrier layer, and a second P-type gallium nitride layer. The first P-type gallium nitride layer is disposed on the first barrier layer. The second barrier layer is disposed on the first P-type gallium nitride layer. The second P-type gallium nitride layer is disposed on the second barrier layer. A width of the second P-type gallium nitride layer is smaller than a width of the first P-type gallium nitride layer. The spacer is disposed on a sidewall of the second P-type gallium nitride layer.