PHOTONICS CHIPS INCLUDING A FULLY-DEPLETED SILICON-ON-INSULATOR FIELD-EFFECT TRANSISTOR

Structures for a photonics chip that include a fully-depleted silicon-on-insulator field-effect transistor and related methods. A first device region of a substrate includes a first device layer, a first portion of a second device layer, and a buried insulator layer separating the first device layer from the first portion of the second device layer. A second device region of the substrate includes a second portion of the second device layer. The first device layer, which has a thickness in a range of about 4 to about 20 nanometers, transitions in elevation to the second portion of the second device layer with a step height equal to a sum of the thicknesses of the first device layer and the buried insulator layer. A field-effect transistor includes a gate electrode on the top surface of the first device layer. An optical component includes the second portion of the second device layer.