A semiconductor structure includes a trench isolation structure and a trench capping layer positioned over the trench isolation structure, wherein the trench isolation layer includes a first electrically insulating material and the trench capping layer includes a second electrically insulating material that is different from the first electrically insulating material. The semiconductor structure also includes a gate structure having a gate insulation layer and a gate electrode positioned over the gate insulation layer, wherein the gate insulation layer includes a high-k material and the gate structure includes a first portion that is positioned over the trench capping layer. A sidewall spacer is positioned adjacent to the gate structure, wherein a portion of the sidewall spacer is positioned on the trench capping layer and contacts the trench capping layer laterally of the gate insulation layer.