Semiconductor devices and data storage systems including the same

A semiconductor device, comprising:

• a substrate having first and second regions;
• a first stack structure including lower gate electrodes stacked and spaced apart from each other in a first direction perpendicular to an upper surface of the substrate in the first region;
• a first channel structure penetrating through the first stack structure;
• a second stack structure on the first stack structure and the first channel structure and including upper gate electrodes stacked and spaced apart from each other in the first direction;
• a second channel structure penetrating through the second stack structure and connected to the first channel structure;
• a first mold structure including lower horizontal sacrificial layers stacked and spaced apart from each other in the first direction in the second region;
• an alignment structure penetrating through the first mold structure;
• and
• a second mold structure on the first mold structure and the alignment structure and including upper horizontal sacrificial layers stacked and spaced apart from each other in the first direction,
• wherein a distance between an uppermost lower gate electrode among the lower gate electrodes and an upper end of the first channel structure is less than a distance between an uppermost lower horizontal sacrificial layer among the lower horizontal sacrificial layers and an upper end of the alignment structure in the first direction.

A data storage system, comprising:

• a semiconductor storage device including a substrate having first and second regions, circuit devices on one side of the substrate, and input/output pads electrically connected to the circuit devices;
• and
• a controller electrically connected to the semiconductor storage device through the input/output pads and controlling the semiconductor storage device,
• wherein the semiconductor storage device further includes:
• a first stack structure including lower gate electrodes stacked and spaced apart from each other in a first direction perpendicular to an upper surface of the substrate in the first region;
• a first channel structure penetrating the first stack structure and in contact with the substrate;
• a second stack structure on the first stack structure and the first channel structure and including upper gate electrodes stacked and spaced apart from each other in the first direction;
• a second channel structure penetrating through the second stack structure and connected to the first channel structure;
• a first mold structure including lower horizontal sacrificial layers stacked and spaced apart from each other in the first direction in the second region;
• an alignment structure penetrating through the first mold structure and in contact with the substrate;
• and
• a second mold structure on the first mold structure and the alignment structure and including upper horizontal sacrificial layers stacked and spaced apart from each other in the first direction, and
• wherein the number of the lower horizontal sacrificial layers is less than the number of the lower gate electrodes.