Nitride semiconductor structure

A nitride semiconductor structure including a silicon substrate, a nucleation layer, a discontinuous defect blocking layer, a buffer layer and a nitride semiconductor layer is provided. The nucleation layer disposed on the silicon substrate, wherein the nucleation layer has a defect density d1. A portion of the nucleation layer is covered by the discontinuous defect blocking layer. The buffer layer is disposed on the discontinuous defect blocking layer and a portion of the nucleation layer that is not covered by the discontinuous defect blocking layer. The nitride semiconductor layer is disposed on the buffer layer. A ratio of a defect density d2 of the nitride semiconductor layer to the defect density d1 of the nucleation layer is less than or equal to about 0.5, at a location where about 1 micrometer above the interface between the nitride semiconductor layer and the buffer layer.