Embodiments relate to a semiconductor device structure including a first channel layer having a first surface and a second surface, a second channel layer having a first surface and a second surface, and the first and second channel layers are formed of a first material. The structure also includes a first dopant suppression layer in contact with the second surface of the first channel layer, and a second dopant suppression layer parallel to the first dopant suppression layer. The second dopant suppression layer is in contact with the first surface of the second channel layer, and the first and second dopant suppression layers each comprises carbon or fluorine. The structure further includes a gate dielectric layer in contact with the first and second dopant suppression layers and the first surface of the first channel layer, and a gate electrode layer disposed on the gate dielectric layer.