Microresonator

1. A microresonator comprising a resonant element and at least one activation electrode placed close to the resonant element, in which the resonant element is placed in an opening of a semiconductor layer covering a substrate, the activation electrode being formed in the semiconductor layer and facing said opening, wherein the resonant element is made of single-crystal silicon.

2. The microresonator of claim 1 , wherein the resonant element has the shape of a mushroom having a foot attached to the substrate.

3. The microresonator of claim 1 , further comprising a vertical detection transistor comprising a stack of three doped semiconductor areas formed in the semiconductor layer and facing said opening, the lower and upper doped semiconductor areas forming source and drain areas of a first doping type, the intermediary semiconductor area forming a “substrate” area of a second doping type, the resonant element forming the transistor gate.

4. A microresonator comprising:

a substrate;

a semiconductor layer on the substrate, the semiconductor layer having an opening;

a single-crystal resonant element formed in the opening, the resonant element having a portion attached to the substrate; and

at least one activation electrode spaced from the resonant element.

5. A microresonator as defined in claim 4 , wherein the at least one activation electrode comprises first and second activation electrodes located on opposite sides of the resonant element.

6. A microresonator as defined in claim 5 , wherein the first and second activation electrodes are formed in the semiconductor layer.

7. A microresonator as defined in claim 4 , wherein the resonant element covers the opening in the semiconductor layer.

8. A microresonator as defined in claim 4 , wherein the resonant element includes an upper portion in spaced relation to the at least one activation electrode and a lower portion, smaller than the upper portion, attached to the substrate.

9. A microresonator as defined in claim 4 , wherein the spacing between the at least one activation electrode and the resonant element is a few tens of nanometers.

10. A microresonator as defined in claim 4 , wherein the at least one activation electrode comprises a heavily-doped area of the semiconductor layer.

11. A microresonator as defined in claim 4 , wherein the at least one activation electrode is located in a wall of the opening in the semiconductor layer.

12. A microresonator as defined in claim 4 , further comprising a vertical detection transistor including upper, intermediate and lower doped semiconductor areas formed in the semiconductor layer and facing the opening in the semiconductor layer, the upper and lower doped semiconductor areas forming source and drain areas of a first doping type, the intermediate doped semiconductor area having a second doping type, and the resonant element forming a transistor gate.

13. A microresonator as defined in claim 4 , wherein the single-crystal resonant element comprises single-crystal silicon.

14. A microresonator as defined in claim 4 , wherein the opening in the semiconductor layer comprises a circular opening.

15. A microresonator as defined in claim 4 , wherein the opening in the semiconductor layer comprises a rectangular opening.