Method of fabricating a modulator of the propagation losses and of the index of propagation of an optical signal

A method of fabricating a modulator of propagation losses and of index of propagation of a guided optical signal, the method comprising:

• providing a stack comprising, successively, a base substrate, a buried layer of first dielectric material, and a semiconductor layer, thickness at every point of the buried layer being equal to e2ini to within approximately 5 nm, wherein e2ini is a constant equal to an average thickness of the buried layer;
• then
• etching the semiconductor layer to form a first electrode of the modulator, the first electrode including a proximal end, a distal end, and an intermediate part extending from the proximal end to the distal end to mechanically and electrically connect the proximal end and the distal end, then
• encapsulating the semiconductor layer in a second dielectric material;
• then
• bonding a substrate onto the encapsulated semiconductor layer;
• then
• forming a second electrode of the modulator having a proximal end facing the proximal end of the first electrode, the proximal end of the first electrode and the proximal end of the second electrode being separated from each other only by a third dielectric layer, the proximal end of the first electrode, the proximal end of the second electrode, and the third dielectric layer forming a waveguide to guide the optical signal to be modulated;
• wherein following the bonding of the substrate onto the encapsulated semiconductor layer and prior to the forming of the second electrode, the method comprises removing the base substrate to expose one face of the buried layer without modifying the thickness of the buried layer by more than 5 nm;
• and
• the forming the second electrode is implemented directly on the exposed face of the buried layer such that, once the second electrode has been formed, the buried layer forms the third dielectric layer interposed between the proximal end of the first electrode and the proximal end of the second electrode.