Stacked structure for a vertical memory device

A stacked structure for a vertical memory device, the stacked structure comprising:

• a first structure on a substrate, the first structure including a pad layer, a first sacrificial layer and a support layer sequentially stacked on the substrate in a vertical direction perpendicular to an upper surface of the substrate, the first sacrificial layer including germanium;
• a second structure on the first structure, the second structure including an insulation layer and a second sacrificial layer alternately and repeatedly stacked on the first structure, the second sacrificial layer including a nitride, such that the first sacrificial layer and the second sacrificial layer include different materials from each other;
• and
• a channel extending through the first and second structures,
• wherein a thickness of the first structure in the vertical direction is less than a thickness of the second structure in the vertical direction.