Abstract: A method for fabricating an active device comprises the steps of injecting particles into a single crystal substrate of a semiconductor material at a predetermined depth from the surface, annealing the substrate that contains the particles to form an insulator layer within the substrate, generally in correspondence to the predetermined depth, the step of annealing including a step of forming a single crystal semiconductor layer of a semiconductor material identical in composition with the substrate, on the insulator layer that is formed by the annealing, starting a deposition of a layer of an oxide superconductor on the semiconductor layer, growing the oxide superconductor layer while maintaining an epitaxial relationship with respect to the substrate; and converting the semiconductor layer to an oxide layer simultaneously to the growth of the oxide superconductor layer.