Structures and formation methods of a semiconductor device structure are provided. The semiconductor device structure includes a fin structure over a semiconductor substrate. The semiconductor device structure also includes active gate stacks over the fin structure. The semiconductor device structure further includes a dummy gate stack over the fin structure. The dummy gate stack is between the active gate stacks. In addition, the semiconductor device structure includes spacer elements over sidewalls of the dummy gate stack and the active gate stacks. The semiconductor device structure also includes an isolation feature below the dummy gate stack, the active gate stacks and the spacer elements. The isolation feature extends into the fin structure from the bottom of the dummy gate stack such that the isolation feature is surrounded by the fin structure.