FETS and Methods of Forming FETS

A FinFET device, comprising:

• a plurality of fins formed in a substrate the fins comprising a gate region and a source/drain region;
• a dielectric over the fins in the gate region, the dielectric comprising a silicon-based oxide that includes germanium;
• an upper fin portion over the dielectric;
• isolation material deposited in trenches between the fins, wherein in the gate region the isolation material is deposited between the dielectric and has an uppermost surface higher than an uppermost surface of the dielectric region but lower than an uppermost surface of the upper fin portion, and wherein in the source/drain region, the isolation material projects laterally from the isolation material in the gate region having a cross-sectional profile in the source/drain region similar to a cross-sectional profile in the gate region;
• a gate structure over the upper fin portion in the gate region, the gate structure in contact with exposed surfaces of the upper fin portion that are exposed from the isolation material, the gate structure defining a channel region in the upper portion, the gate structure comprising a gate dielectric and gate material over the gate dielectric;
• and
• source/drain structure in the source drain region, extending laterally from the gate region and formed over the plurality of fins, wherein a bottom surface of the source/drain structure is lower than uppermost surface of the isolation material.

A method, comprising:

• forming a first layer of a first material over a substrate;
• forming a second layer of a second material over the first layer;
• recessing, through the first layer and the second layer, the substrate to form at least one fin and a trench on either side of the fin, the at least one fin comprising a lower portion made from the recessed substrate, a middle portion made from the first layer, and an upper portion made from the second layer;
• oxidizing the first material to transform at least a portion of the first material into a third material;
• oxidizing sidewalls of the upper portion to transform a portion of the second material into a fourth material;
• oxidizing a top portion of the sidewalls of the lower portion to transform the top portion into a fifth material;
• depositing an isolation material into the trenches;
• planarizing an uppermost surface of the isolation material to be coplanar with an uppermost surface of the upper portion;
• following the planarizing, recessing the isolation material such that the uppermost surface of the isolation material is above an interface of the middle portion and upper portion of the fin;
• forming a gate structure over the fin, a portion of the fin under the gate structure comprising a gate region and a portion of the fin not under the gate structure comprising a drain/source region;
• in the drain/source region, etching the fin to remove the upper portion and middle portion;
• and
• in the drain/source region, epitaxially forming a drain/source contact over the lower portion of the fin.