Isolation method capable of using a re-growth process of a semi-insulating film improves isolation characteristics of the element isolation by a semiconductor element (isolation) are disclosed. The present invention is a layer a buffer layer, a channel on a compound semiconductor substrate, a spacer layer, and a step of growing successively the schottky layer and the ohmic layer, to a predetermined portion of the substrate using a mask pattern for defining an active region on the results the etched isolation so as to planarize Sikkim as well as block the leakage current path of the etched active region side portion of the step of the step for obtaining a vertical etch section by etching the respective layers in order to isolate the defined region and the active region the step of selectively re-grown in the semi-insulating film in the region and, after removing the mask pattern after exposing a portion of a step, a schottky layer of the active region to form an ohmic metal layer on the source and drain regions connected between the exposed schottky layer obtain a gate electrode and a step of forming the source and drain electrodes for connection with the ohmic metal layer for It is.