Techniques for forming uniform fin height on oxide substrates for finFET devices is provided. In one aspect, a method for forming a finFET device includes: patterning fins in a wafer; burying the fins in an oxide material; recessing the oxide material to form a recessed oxide material in between the fins; selectively forming sidewall spacers, above the recessed oxide material, alongside top portions of one or more of the fins that serve as active fins of the finFET device; converting bottom portions of the one or more fins beneath the sidewall spacers to an oxide, such that the active fins are present on the oxide; and forming gates over the active fins. A finFET device is also provided.