Semiconductor device and manufacturing method of semiconductor device

A semiconductor device, comprising:

• a gate stack with conductive layers and insulating layers that are stacked alternately with each other;
• an insulating core passing through the gate stack, and including an air gap;
• a first channel pattern passing through the gate stack, and surrounding a portion of the insulating core;
• a second channel pattern coupled to the first channel pattern and surrounding another portion of the insulating core, the second channel pattern protruding above a top surface of the gate stack;
• a gate liner having a first portion and a second portion, wherein the first portion covers the top surface of the gate stack except a portion surrounded by the first channel pattern, and the second portion surrounds a portion of a sidewall of the second channel pattern;
• and
• an isolation insulating layer passing through the gate liner,
• wherein a gate insulating layer is disposed between a side wall of the second channel pattern and the gate liner.