Semiconductor device structure and methods of forming the same

A semiconductor device structure, comprising:

• a first semiconductor layer disposed over a substrate, wherein the first semiconductor layer has a first end and a second end opposite the first end;
• an epitaxial feature disposed over the substrate, wherein the epitaxial feature is electrically connected to the first end of the first semiconductor layer;
• a contact etch stop layer disposed over the substrate, wherein the contact etch stop layer interfaces the second end of the first semiconductor layer;
• an interlayer dielectric layer disposed on and interfacing the contact etch stop layer;
• and
• a bottom of the epitaxial feature is located at a same level as a bottom of the contact etch stop layer.

A method for forming a semiconductor device structure, comprising:

• forming a sacrificial gate electrode over a portion of a stack of semiconductor layers;
• recessing exposed portions of the stack of semiconductor layers not covered by the sacrificial gate electrode to expose first and second well portions;
• removing edge portions of second semiconductor layers of the stack of semiconductor layers to create cavities;
• forming a first dielectric layer on the first and second well portions and in the cavities;
• forming a mask layer on a portion of the first dielectric layer disposed on the first well portion;
• removing a portion of the first dielectric layer not covered by the mask layer to expose the second well portion;
• and
• forming an epitaxial feature over the second well portion.