The present disclosure provides a semiconductor structure, including a substrate, a first III-V layer over the substrate, having a first band gap, and a second III-V layer over the first III-V layer, having a second band gap. The second III-V layer includes a first surface in contact with the first III-V layer and a second surface opposite to the first surface. The second band gap at the second surface is greater than the second band gap at the first surface. The present disclosure also provides a manufacturing method of the aforesaid semiconductor structure.