Example embodiments provide triple-gate semiconductor devices isolated by reverse shallow trench isolation (STI) structures and methods for their manufacture. In an example process, stacked layers including a form layer over a dielectric layer can be formed over a semiconductor substrate. One or more trenches can be formed by etching through the stacked layers. The one or more trenches can be filled by an active area material to form one or more active areas, which can be isolated by remaining portions of the dielectric layer. Bodies of the active area material can be exposed by removing the form layer. One or more triple-gate devices can then be formed on the exposed active area material. The example triple-gate semiconductor devices can control the dimensions for the active areas and provide less isolation spacing between the active areas, which optimizes manufacturing efficiency and device integration quality.