An isolated gate field effect transistor and the manufacture method thereof. The isolated gate field effect transistor includes a substrate; a nitride transistor structure arranged on the substrate; a dielectric layer on the nitride transistor structure, where the dielectric layer includes a first dielectric layer, a second dielectric layer and a third dielectric layer and material of the second dielectric layer includes metal; a groove formed in a gate region and at least partially through the dielectric layer; a metal gate formed in the groove; and a source electrode and a drain electrode located at two ohmic contact regions.