A method for manufacturing components on a mixed substrate. The method comprises the following steps: providing a substrate of the semiconductor-on-insulator (SeOI) type comprising a buried oxide layer between a supporting substrate and a thin layer, forming in this substrate a plurality of trenches opening out at a free surface of the thin layer and extending over a depth such that each trench passes through the thin layer and the buried oxide layer, these primary trenches delimiting at least one island of the SeOI substrate, forming a mask inside the primary trenches and as a layer covering the areas of the free surface of the thin layer located outside the islands, proceeding with heat treatment for dissolving the buried oxide layer present at the island, so as to reduce the thickness thereof.