The embodiments described herein are directed to a method for reducing fin oxidation during the formation of fin isolation regions. The method includes providing a semiconductor substrate with an n-doped region and a p-doped region formed on a top portion of the semiconductor substrate; epitaxially growing a first layer on the p-doped region; epitaxially growing a second layer different from the first layer on the n-doped region; epitaxially growing a third layer on top surfaces of the first and second layers, where the third layer is thinner than the first and second layers. The method further includes etching the first, second, and third layers to form fin structures on the semiconductor substrate and forming an isolation region between the fin structures.