Depletion type GaN device and preparation method thereof

The invention discloses a depletion type GaN device and a preparation method thereof, the depletion type GaN device comprises a source electrode, a drain electrode, a gate electrode, an independent electrode, and a substrate, a laminated structure and a dielectric layer which are sequentially arranged from bottom to top, and the source electrode, the drain electrode and the independent electrode are all located in the laminated structure and the dielectric layer; the laminated structure comprises a nucleating layer, a buffer layer, a channel layer, a barrier layer and a cap layer which are sequentially arranged from bottom to top; an electrical isolation region is arranged below the source electrode, two-dimensional electron gas in the electrical isolation region is electrically isolated from two-dimensional electron gas outside the electrical isolation region, and one end of the electrical isolation region is connected with the independent electrode; and the independent electrode is also connected with the g