Transistor fins with different thickness gate dielectric

An integrated circuit device comprising:

• a first fin-type field effect transistor (finFET) and a second finFET laterally adjacent one another extending from a surface of an isolation layer, wherein the first finFET has a first fin structure and the second finFET has a second fin structure;
• an insulator layer on the first fin structure and the second fin structure;
• a gate conductor intersecting the first fin structure and the second fin structure, wherein at least the insulator layer separates the gate conductor from the first fin structure and the second fin structure;
• a work function metal layer between the gate conductor and the insulator layer;
• and
• source and drain structures on the first fin structure and the second fin structure laterally adjacent the gate conductor,
• wherein the first fin structure has sidewalls that include a step and the second fin structure has sidewalls that do not include the step, and
• wherein the step is approximately parallel to the surface of the isolation layer.

An integrated circuit device comprising:

• a substrate;
• an isolation layer on the substrate, wherein the isolation layer has a surface opposite where the isolation layer contacts the substrate, and wherein the isolation layer has a first area separated from a second area;
• first fin-type field effect transistors (finFETs) in the first area of the isolation layer, wherein the first finFETs have first fin structures extending from the substrate through the isolation layer and extending external to the isolation layer;
• second finFETs in the second area of the isolation layer, wherein the second finFETs have second fin structures extending from the substrate through the isolation layer and extending external to the isolation layer;
• an insulator layer on the first fin structures and the second fin structures, wherein the insulator layer comprises a first portion on the first fin structures and a second portion on the second fin structures, and wherein the first portion of the insulator layer is thicker than the second portion of the insulator layer;
• a gate conductor intersecting the first fin structures and the second fin structures, wherein at least the insulator layer separates the gate conductor from the first fin structures and the second fin structures;
• and
• source and drain structures on the first fin structures and the second fin structures laterally adjacent the gate conductor,
• wherein the first fin structures have sidewalls that include a step at a location where the first fin structures intersect the surface of the isolation layer,
• wherein the second fin structures have sidewalls that do not include the step, and
• wherein the step is approximately parallel to the surface of the isolation layer.