to the crystals of the quantum well bexes in the interface between the surface of the substrate and the quantum well boxes which cannot be avoided in the prior art of electron beam lithography forms electron traps or energy levels in energy band gaps and greatly affect the development of the quantum effect adversely however in the quantum effective device prepared by the method of this invention the quantum well boxes have a uniform size and the crystals of the quantum well boxes existing in the interface between the quantum well boxes and the surface of the substrate have no defects and the device develops a quantum size effect effectively for example when the quantum effective device is applied to a semiconductor laser the value of the full width at half maximum in the spectrum of the emitted light becomes narrow and the efficiency for light emission is expected to be improved the presence of quantum well boxes in the quantum effective device of this invention can be ascertained by photoluminescence or infrared high resolution far infrared fourier transformation spectroscopy using modulated photoconductivity technique method for example if the quantum well boxes are composed of a gaas system the amount.