一种半导体组件，其包括基底。半导体组件还包括位于基底上之第一鳍结构及第二鳍结构。半导体组件更包括分别横越于第一鳍结构及第二鳍结构上之第一闸极电极及第二闸极电极。此外，半导体组件包括介于第一鳍结构与第一闸极电极之间，且介于第二鳍结构与第二闸极电极之间的闸极介电层。再者，半导体组件包括位于基底上之虚置闸极电极。虚置闸极电极位于第一闸极电极与第二闸极电极之间，且虚置闸极电极之较高部分宽于虚置闸极电极之较低部分。

Embodiments of mechanisms for forming a semiconductor device are provided. The semiconductor device includes a substrate. The semiconductor device also includes a first fin and a second fin over the substrate. The semiconductor device further includes a first gate electrode and a second gate electrode traversing over the first fin and the second fin, respectively. In addition, the semiconductor device includes a gate dielectric layer between the first fin and the first gate electrode and between the second fin and the second gate electrode. Further, the semiconductor device includes a dummy gate electrode over the substrate, and the dummy gate electrode is between the first gate electrode and the second gate electrode. An upper portion of the dummy gate electrode is wider than a lower portion of the dummy gate electrode.