There is provided a compound semiconductor substrate prepared by forming a point defect in an inside structure thereof by implanting an electrically-neutral impurity with energy of 0.1 to 10 MeV on a surface of the substrate. When the compound semiconductor is undoped, electrical resistance increases to increase insulating properties, and when the compound semiconductor is doped with an n-type dopant, the impurity is implanted and charge concentration of the substrate increases to increase conductive properties. In accordance with the present invention, the various electrical properties needed for the compound semiconductor can be effectively controlled by increasing the insulating properties of the undoped compound semiconductor or by increasing the charge concentration of the n-type compound semiconductor, and the application range to various devices can be expanded.