A method includes measuring a depth of a shallow trench isolation (STI) region below a surface of a substrate. The STI region is filled with an oxide material. The substrate has a nitride layer above the surface. A thickness of the nitride layer is measured. A first chemical vapor etch (CVE) of the oxide material is performed, to partially form a recess in the STI region. The first CVE removes an amount of the oxide material less than the thickness of the nitride layer. The nitride layer is removed by dry etching. A remaining height of the STI region is measured after removing the nitride. A second CVE of the oxide material in the STI region is performed, based on the measured depth and the remaining height, to form at least one fin having a desired fin height above the oxide in the STI region without an oxide fence.