Abstract: A stacked semiconductor device includes a first gate structure formed on a substrate, a first insulating interlayer covering the first gate structure on the substrate, a first active pattern formed through and on the first insulating interlayer and contacting the substrate, a second gate structure formed on the first active pattern and the first insulating interlayer, a buffer layer covering the second gate structure on the first active pattern and the first insulating interlayer, a second insulating interlayer formed on the buffer layer, and a contact plug formed through the first and second insulating interlayers, which contacts with the substrate and is insulated from the second gate structure by the buffer layer. Operation failures of a transistor in the stacked semiconductor device can be reduced because the buffer layer prevents a word line from being electrically connected to the contact plug.

Abstract: A stacked semiconductor device includes a first gate structure formed on a substrate, a first insulating interlayer covering the first gate structure on the substrate, a first active pattern formed through and on the first insulating interlayer and contacting the substrate, a second gate structure formed on the first active pattern and the first insulating interlayer, a buffer layer covering the second gate structure on the first active pattern and the first insulating interlayer, a second insulating interlayer formed on the buffer layer, and a contact plug formed through the first and second insulating interlayers, which contacts with the substrate and is insulated from the second gate structure by the buffer layer. Operation failures of a transistor in the stacked semiconductor device can be reduced because the buffer layer prevents a word line from being electrically connected to the contact plug.