Oxide isolated fin-type field-effect transistors

A method of forming a semiconductor structure, the method comprising:

• forming a plurality of fins on a layered substrate comprising a semiconductor substrate, a top fin portion layer, and a sacrificial layer located in between the semiconductor substrate and the top fin portion layer;
• wherein the sacrificial layer comprises a silicon germanium;
• selectively etching the sacrificial layer to form recesses in an x-direction perpendicular to a height of the plurality of fins;
• depositing a germanium oxide layer on the plurality of fins and in the recesses;
• annealing the structure in an inert environment to reduce the germanium oxide in the germanium oxide layer and oxidize the silicon in the sacrificial layer to form a concentrated germanium region located in between oxidized regions in the ex-direction perpendicular to the height of the plurality of fins;
• wherein the concentrated germanium region has a higher concentration of germanium than the lower concentration of germanium in the sacrificial layer and the oxidized regions comprise silicon oxide;
• and
• oxidizing the structure to convert the germanium in the concentrated germanium region to silicon germanium oxide thereby forming a mixed oxide region located in between the oxidized regions.