Abstract
A semiconductor device structure is provided. The semiconductor device structure includes a semiconductor substrate. The semiconductor device structure includes a first gate stack positioned over the semiconductor substrate. The semiconductor device structure includes a first doped structure and a second doped structure positioned at two opposite sides of the first gate stack and embedded in the semiconductor substrate. The semiconductor device structure includes a second gate stack positioned over the semiconductor substrate and adjacent to the second doped structure. The semiconductor device structure includes a third gate stack positioned over the semiconductor substrate. The semiconductor device structure includes an isolation structure embedded in the semiconductor substrate and between the second gate stack and the third gate stack. The isolation structure is wider and thinner than the second doped structure, and the isolation structure is made of an epitaxial material.