Device isolation using preferential oxidation of the bulk substrate

A structure, comprising:

• a semiconductor substrate;
• a semiconductor buffer layer disposed on the substrate;
• an oxide layer disposed on the buffer layer;
• and
• a first fin and a second fin, each comprising a semiconductor material disposed on the oxide layer,
• wherein said first fin, said second fin, and said buffer layer are epitaxially aligned to said substrate,
• wherein the oxide layer continuously extends from below a bottom surface of the first fin to below a bottom surface of the second fin,
• wherein the oxide layer extends between a side surface of the first fin and a side surface of the second fin such that a thickness of the oxide layer extending between the first fin and the second fin is more than the thickness of the oxide layer extending between a top surface of buffer layer and the bottom surface of the first fin, and
• wherein the first fin comprises a III-V semiconductor having an oxidation rate less than an oxidation rate of the buffer layer.