US Patent 7977725 Integrated circuit semiconductor device including stacked level transistors

An integrated circuit semiconductor device includes a first transistor formed at a lower substrate and configured with at least one of a vertical transistor and a planar transistor. A bonding insulation layer is formed on the first transistor, and an upper substrate is bonded on the bonding insulation layer. A second transistor configured with at least one of a vertical transistor and a planar transistor is formed at the upper substrate. The first transistor and the second transistor are connected by an interconnection layer.