A high electron mobility transistor includes a channel layer, a barrier layer, a first compound semiconductor layer, and a second compound semiconductor layer. The channel layer is disposed on the substrate, and the barrier layer is disposed on the channel layer. The first compound semiconductor layer is disposed on the barrier layer. The second compound semiconductor layer is disposed between the barrier layer and the first compound semiconductor layer, where the first compound semiconductor layer and the second compound semiconductor layer include a concentration distribution of metal dopant, and the concentration distribution of metal dopant includes a first peak in the first compound semiconductor layer and a second peak in the second compound semiconductor layer.