A semiconductor structure includes a fin active region extruded from a semiconductor substrate; and a gate stack disposed on the fin active region. The gate stack includes a gate dielectric layer and a gate electrode disposed on the gate dielectric layer. The gate dielectric layer includes a first dielectric material. The semiconductor structure further includes a dielectric gate of a second dielectric material disposed on the fin active region. The gate dielectric layer extends from a sidewall of the gate electrode to a sidewall of the dielectric gate. The second dielectric material is different from the first dielectric material in composition.