FinFET device and method of forming the same are provided. The method of forming the FinFET device includes the following steps. A substrate having a plurality of fins is provided. An isolation structure is on the substrate surrounding lower portions of the fins. A hybrid fin is formed aside the fins and on the isolation structure. A plurality of gate lines and a dielectric layer are formed. The gate lines are across the fins and the hybrid fin, the dielectric layer is aside the gate lines. A portion of the gate lines is removed, so as to form first trenches in the dielectric layer and in the gate lines, exposing a portion of the hybrid fin and a portion of the fins underlying the portion of the gate lines. The portion of the fins exposed by the first trench and the substrate underlying thereof are removed, so as to form a second trench under the first trench. An insulating structure is formed in the first trench and the second trench.