Non-planar transistor structures and methods of manufacturing thereof

A method for fabricating semiconductor devices, comprising:

• forming a first fin structure and a second fin structure in a first region and a second region of a substrate, respectively, wherein the first and second fin structure and the substrate comprise a first semiconductor material;
• forming a first liner structure and a second liner structure at least extending along sidewalls of the first fin structure and sidewalls of the second fin structure, respectively;
• replacing an upper portion of the second fin structure with a second semiconductor material, while leaving the first fin structure substantially intact;
• and
• exposing a top surface and upper sidewalls of the first fin structure, and a top surface and upper sidewalls of the second fin structure.

A method for fabricating semiconductor devices, comprising:

• forming a fin structure protruding from a substrate, wherein the fin structure and the substrate comprise a first semiconductor material;
• forming a liner structure extending along sidewalls of the fin structure and overlaying a top surface of the fin structure;
• removing a portion of the liner structure overlaying the top surface and then an upper portion of the fin structure;
• epitaxially growing, from a lower portion of the fin structure, a second semiconductor material as a replacement upper portion of the fin structure, the second semiconductor material being different from the first semiconductor material;
• exposing upper sidewalls of the fin structure;
• and
• forming a gate structure straddling the fin structure.