Capacitive optical modulator

A capacitive electro-optical modulator comprising:

• a silicon-on-insulator substrate that includes a silicon layer and an underlying insulating layer;
• a germanium or silicon-germanium strip overlying the silicon layer;
• a silicon strip overlying the germanium or silicon-germanium strip, the silicon strip being wider than the germanium or silicon-germanium strip;
• an insulator laterally adjacent the germanium or silicon-germanium strip and the silicon strip and having an upper surface that is flush with an upper surface of the silicon strip, a first portion of a lower surface of the insulator separated from the underlying insulating layer of the silicon-on-insulator substrate by the silicon layer and a second portion of the lower surface of the insulator abuts the underlying insulating layer of the silicon-on-insulator substrate;
• an upper insulating layer overlying the insulator and the silicon strip;
• and
• a layer of III-V material overlying the upper insulating layer, the layer of III-V material formed as a third strip arranged facing the silicon strip and separated therefrom by a portion of the upper insulating layer.