Semiconductor device structure and methods of forming the same

A method, comprising:

• forming first and second fin structures, wherein the first fin structure comprises a first semiconductor layer and a second semiconductor layer disposed over the first semiconductor layer, and the second fin structure comprises a third semiconductor layer and a fourth semiconductor layer disposed over the third semiconductor layer;
• increasing dimensions of the first and second semiconductor layers without increasing dimensions of the third and fourth semiconductor layers;
• depositing a gate dielectric layer surrounding the first, second, third, and fourth semiconductor layers;
• forming a first gate electrode layer surrounding the first and second semiconductor layers;
• and
• forming a second gate electrode layer surrounding the third and fourth semiconductor layers.

A method, comprising:

• forming first and second fin structures, wherein the first fin structure comprises alternating first and second semiconductor layers, and the second fin structure comprises alternating third and fourth semiconductor layers;
• removing the second and fourth semiconductor layers to expose the first and third semiconductor layers;
• increasing dimensions of the first semiconductor layer without increasing dimensions of the third semiconductor layer;
• depositing a gate dielectric layer surrounding the first and third semiconductor layers;
• forming a first gate electrode layer surrounding the first semiconductor layer;
• and
• forming a second gate electrode layer surrounding the third semiconductor layer.