Method for insulating AlGaN / GaN HEMT device

The invention discloses an isolation method for an AlGaN/GaN HEMT device, belonging to the microelectronic technical field. The invention aims to avoid material damage in the isolation technology of the prior device by adoption of the method. The method is realized as follows: selective epitaxial growth GaN base materials are taken as the core; a spacer medium film is deposited on a sapphire or aSic substrate at first; the spacer medium film is selectively etched according to a design mask, and areas of the medium film which are exposed out of the substrate surface are removed, namely a windowarea is an active area of the device and the spacer medium film is kept on the outside of the active area; growth of a GaN epitaxial layer and an AlGaN/GaN heterostructure is continued by adoption of the MOCVD technology; the AlGaN/GaN heterostructure only grows in the window area and the surface of a medium film area is only provided with GaN polycrystalline particles and AlGaN polycrystallinepa rticles, thereby isolati