FETS and Methods of Forming FETS

A method comprising:

• epitaxially growing a first crystalline semiconductor material on a substrate;
• epitaxially growing a second crystalline semiconductor material above the first crystalline semiconductor material;
• patterning the first crystalline semiconductor material and the second crystalline semiconductor material to form a first fin on the substrate;
• oxidizing all of the first crystalline semiconductor material in the first fin to form a first oxide material, and oxidizing a portion of the second crystalline semiconductor material in the first fin to form a second oxide material;
• forming isolation regions on the substrate and surrounding the first oxide material of the first fin;
• forming a gate structure over the first fin and the isolation regions;
• and
• forming source/drain regions on opposing sides of the gate structure.

A semiconductor device, comprising:

• a first semiconductor strip disposed on a substrate;
• a second semiconductor strip disposed on the substrate, wherein a channel region of the first semiconductor strip comprises:
• a bottom portion disposed on the substrate comprising the same material as the substrate,
• a middle portion comprising a first crystalline semiconductor material and a first oxide material, the first oxide material covering side portions of the first crystalline semiconductor material, and
• a top portion comprising a second crystalline semiconductor material;
• an isolation region disposed between the first semiconductor strip and the second semiconductor strip, the isolation region having a top surface which is lower than a top surface of the first semiconductor strip and higher than an interface of the second crystalline semiconductor material and the first crystalline semiconductor material in the first semiconductor strip;
• and
• a gate structure formed over the channel region of the first semiconductor strip.