GaN HEMT device and preparation method thereof

The invention is suitable for the technical field of high electron mobility transistors, and provides a GaN HEMT device and a preparation method. The preparation method comprises the following steps: forming a SiN protection layer on a GaN epitaxial layer, and forming a SiO2 gate region on the SiN protection layer; carrying out ion implantation by taking the SiO2 gate region as a mask, and forming a source region and a drain region on the GaN epitaxial layer; planarization layers are formed on the two sides of the SiO2 gate region, and the heights of the SiO2 gate region and the planarization layers are etched to preset heights; siO2 in the SiO2 gate region is removed, and a gate groove structure is formed; filling SiN in the part, close to the groove wall, of the gate groove structure to form a side wall, and obtaining a gate groove with a preset size; and forming a metal gate in the gate groove. According to the GaN HEMT device with the gate and source-drain self-aligned structure, various parasitic paramet