A shallow trench isolation (STI) structure is formed from a conventional STI trench structure formed of first dielectric material extending into the substrate. The conventional STI structure undergoes further processing, including removing a first portion of the dielectric material and adjacent portions of the semiconductor substrate to create a first recess, and then removing another portion of the dielectric material to create a second recess in just the dielectric material. A nitride layer is formed above remaining dielectric material and on the sidewalls of the substrate. A second dielectric material is formed on the spacer layer and fills the remainder of first and second recesses. The nitride layer provides an “inner spacer” between the first insulating material and the second insulating material and also separates the substrate from the second insulating material. An isotropic Fin reveal process is performed and the STI structure assists in equalizing fin heights and increasing active S/D region area/volume.