<p>A method of producing a mounted transistor comprising: a step (a) of forming a transistor (100); a step (b) of polishing a formed substrate (101); and a step (c) of securing the transistor (100), the formed substrate (101) of which is polished, to a holding substrate (200). The step (a) comprises sequentially forming a first semiconductor layer and a second semiconductor layer with a band gap larger than the first semiconductor layer on the main surface of the formed substrate (101). The step (b) comprises polishing the surface opposite of the main surface of the formed substrate (101). The step (c) comprises securing the transistor (100) on the holding substrate (200) in a state in which stress is applied to the formed substrate (101) in a direction that makes warping of the formed substrate (101) become smaller.</p>
