According to an embodiment of the present invention, a semiconductor structure includes a semiconductor substrate and a plurality of fins located on the semiconductor substrate. The plurality of fins each independently includes a bottom fin portion, a top fin portion layer, and an isolated oxide layer located in between the bottom fin portion and the top fin portion layer in the y-direction parallel to the height of the plurality of fins. The isolated oxide layer includes a mixed oxide region located in between oxidized regions in an x-direction perpendicular to the height of the plurality of fins.