A semiconductor device includes a gate stack with conductive layers and insulating layers that are stacked alternately with each other, a first channel pattern passing through the gate stack, a second channel pattern coupled to the first channel pattern, the second channel pattern protruding above a top surface of the gate stack, an insulating core formed in the first channel pattern, the insulating core extending into the second channel pattern, a gate liner with a first portion that surrounds a top surface of the gate stack and a second portion that surrounds a portion of a sidewall of the second channel pattern, and a barrier pattern coupled to the gate liner, the barrier pattern surrounding a remaining portion of the sidewall of the second channel pattern.