A semiconductor structure and a method for forming the same are provided. The semiconductor structure comprises a first semiconductor region, a second semiconductor region, a dielectric structure and a gate electrode layer. The first semiconductor region has a first type conductivity. The second semiconductor region has a second type conductivity opposite to the first type conductivity. The first semiconductor region is adjoined to the second semiconductor region. The dielectric structure is on the first semiconductor region and the second semiconductor region. The gate electrode layer is on the dielectric structure.