A method of fabricating a semiconductor structure includes: growing a dielectric layer on a substrate; defining an epitaxial region and a gap region on the dielectric layer; etching a dielectric layer of the epitaxial region to expose the substrate; sequentially growing a gallium nitride buffer layer and an aluminum gallium nitride barrier layer on the exposed substrate. The method of fabricating a semiconductor structure provided by the present application divides the aluminum gallium nitride barrier layer into a plurality of independent portions, thus preventing the microcracks from occurring in the aluminum gallium nitrogen film while increasing the aluminum component, thereby improving the yield rate and reliability of the device.