Semiconductor structure and fabrication method thereof

Abstract

A semiconductor structure is provided. The semiconductor structure includes a substrate with active areas, shallow trench isolation (STI) structures disposed in the substrate, word lines embedded in the substrate, a first barrier layer, work function control structures, and a cap layer. Each word line includes active portions overlapping with corresponding ones of the active areas and passing portions overlapping with corresponding ones of the STI structures. The first barrier layer is disposed on top surfaces of the active portions and top surfaces of the passing portions. The work function control structures are disposed over the first barrier layer and the top surfaces of the active portions. The cap layer includes first portions and second portions. The first portions are located above the active portions. The second portions are located above the passing portions.

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