Abstract: A semiconductor device. The device including: a planar FET formed in a single crystal-silicon substrate, the FET comprising a first channel region, first and second source drains on opposite sides of the first channel region and a gate, the gate over the channel region and electrically isolated from the channel region by a first gate dielectric layer; and a FinFET formed in single crystal silicon block on top of and electrically isolated from the substrate, the FinFET comprising a second channel region, third and fourth source drains on opposite first and second ends of a second channel region and the gate, the gate electrically isolated from the second channel region by a second gate dielectric layer.