A semiconductor power device includes a substrate, a buffer structure formed on the substrate, a barrier structure formed on the buffer structure, a channel layer formed on the barrier structure, and a barrier layer formed on the channel layer. The barrier structure includes a first functional layer on the buffer structure, a first back-barrier layer on the first functional layer, and an interlayer between the first back-barrier layer and the first functional layer. A material of the first back-barrier layer comprises Alx1Ga1-x1N, a material of the first functional layer comprises Alx2Ga1-x2N, 0