In a method of manufacturing a stacked semiconductor device, a seed layer including impurity regions may be prepared. A first insulation interlayer pattern having a first opening may be formed on the seed layer. A first SEG process may be carried out to form a first plug partially filling the first opening. A second SEG process may be performed to form a second plug filling the first opening. A third SEG process may be carried out to form a first channel layer on the first insulation interlayer pattern. A second insulation interlayer may be formed on the first channel layer. The second insulation interlayer, the first channel layer and the second plug arranged on the first plug may be removed to expose the first plug. The first plug may be removed to form a serial opening. The serial opening may be filled with a metal wiring.