Semiconductor device and method of manufacturing semiconductor device

A semiconductor device comprising:

• a support structure including a plurality of first insulating layers alternately stacked with a plurality of second insulating layers;
• a gate structure including a plurality of conductive layers and including a first section positioned at a level corresponding to a level of the support structure and a second section positioned on the support structure;
• a contact plug extending through the gate structure and connected to a first conductive layer of the plurality of conductive layers;
• and
• a first support including a plurality of pillars extending between the first section and the support structure and extending through the second section and a plurality of first protrusions protruding from the plurality of pillars into the support structure.