Single-crystal layer on a dielectric layer

The process relates to the production of a layer of a single-crystal first material on a second material. The second material has at least one aperture exposing a surface portion of a single-crystal third material. The process generally includes forming an at least partially crystalline first layer of said first material on said surface portion of the third material. Then, an amorphous or partially crystalline second layer of the first material is formed on the at least partially crystalline first layer of the first material and on one part of the second material that is around said aperture. Finally, the process includes recrystallization annealing of the first material. Thus, it is possible to produce, within one and the same wafer, either transistors on a germanium-on-insulator substrate with transistors on a silicon-on-insulator substrate, or transistors on a germanium-on-insulator substrate with transistors on a silicon substrate.