A semiconductor structure is provided. The semiconductor structure includes fin structures, a gate structure across the fin structures, and a dielectric layer. The gate structure includes a work function layer over the gate dielectric layer, and a contact layer over the work function layer. A portion of the work function layer is located between the fin structures, and a top surface of the portion is higher than a top surface of the fin structures. A top surface of the work function layer and a top surface of the dielectric layer are substantially on a same level. A method for forming a semiconductor structure is also provided.