US Patent 7741644 Semiconductor device having stacked transistors

A semiconductor device includes a first semiconductor layer, a first interlayer insulation layer, a second semiconductor layer, and a gate pattern. The first interlayer insulation layer covers the first semiconductor layer. The second semiconductor layer is formed on the first interlayer insulation layer and includes source regions, drain regions, and a channel region interposed between the source region and the drain region. The gate pattern includes a gate insulation layer on the channel region of the second semiconductor layer. At least one of the source regions and the drain regions includes an elevated layer having a top surface higher than that of the channel region.