A semiconductor structure, a fabrication method, and a design structure of the same. The semiconductor structure includes (i) a semiconductor substrate which includes a top substrate surface perpendicular to the top substrate surface, (ii) a control gate electrode region and a first semiconductor body region on the semiconductor substrate, and (iii) a second semiconductor body region on the first semiconductor body region. The semiconductor structure further includes (i) a first gate dielectric region sandwiched between the first semiconductor body region and the control gate electrode region and (ii) a second gate dielectric region sandwiched between the second semiconductor body region and the control gate electrode region. The second semiconductor body region overlaps the first semiconductor body region in the reference direction. A first thickness of the first gate dielectric region is different from a second thickness of the second gate dielectric region.