FinFET structure and method for fabricating the same

A method comprising:

• recessing a silicon substrate to form a fin;
• removing an upper portion of the fin to form a trench;
• growing a silicon germanium material in the trench to form a middle portion of the fin;
• forming a first silicon carbon layer over and in contact with the middle portion of the fin;
• forming an upper portion of the fin by growing a silicon material over the first silicon carbon layer;
• replacing an outer portion of the upper portion of the fin with a second silicon carbon layer and a first source/drain region;
• and
• applying a thermal oxidation process to the middle portion of the fin to form an oxide outer layer.

A method comprising:

• forming a fin over a substrate, wherein the substrate is formed of a first semiconductor material and the fin is enclosed by an isolation region;
• recessing the fin to form a trench over a lower portion of the fin;
• growing a second semiconductor material in the trench to form a middle portion of the fin;
• forming a first carbon doped layer over the lower portion of the fin;
• growing the first semiconductor material over the first carbon doped layer to form an upper portion of the fin;
• replacing outer portions of the upper portion of the fin with second carbon doped layers and source/drain regions;
• and
• applying a thermal oxidation process to the middle portion of the fin to form an oxide outer layer.