US Patent 10475791 Transistor fins with different thickness gate dielectric

First and second fin-type field effect transistors (finFETs) are formed laterally adjacent one another extending from a top surface of an isolation layer. The first finFET has a first fin structure and the second finFET has a second fin structure. An insulator layer is on the first fin structure and the second fin structure. A gate conductor intersects the first fin structure and the second fin structure, and at least the insulator layer separates the gate conductor from the first fin structure and the second fin structure. Source and drain structures are on the first fin structure and the second fin structure laterally adjacent the gate conductor. The first fin structure has sidewalls that include a step and the second fin structure has sidewalls that do not include the step. The step is approximately parallel to the surface of the isolation layer.