Semiconductor devices and data storage systems including the same

A semiconductor device, comprising:

• a first substrate structure including a substrate, first circuit devices on the substrate, second circuit devices that extend into the substrate, and a gate isolation layer that extends into the substrate and is between ones of the second circuit devices;
• and
• a second substrate structure electrically connected to the first substrate structure on the first substrate structure, and including gate electrodes electrically connected to the first and second circuit devices,
• wherein adjacent second circuit devices among the second circuit devices are disposed symmetrically with respect to the gate isolation layer.

A data storage system, comprising:

• a semiconductor storage device including a first substrate structure including a substrate and first circuit devices and second circuit devices, a second substrate structure including gate electrodes, and an input/output pad electrically connected to the first and second circuit devices;
• and
• a controller electrically connected to the semiconductor storage device by the input/output pad and configured to control the semiconductor storage device,
• wherein the first circuit devices are on the substrate, and the second circuit devices extend into the substrate,
• wherein the first substrate structure further comprises:
• a gate isolation layer that extends into the substrate and is between ones of the second circuit devices;
• a backside insulating layer on a lower surface of the substrate;
• and
• a lower active contact plug that extends into the backside insulating layer and is electrically connected to the second circuit devices.