Vertical memory structure with air gaps and method for preparing the same

Abstract

The present disclosure provides a vertical memory structure including a semiconductor stack, a contact plug, gate electrodes and air gap structures. The semiconductor stack includes a lower semiconductor pattern structure filling a recess on a substrate and protruding from an upper surface of the substrate in a first direction substantially perpendicular to the upper surface of the substrate. The contact plug is disposed over the lower semiconductor patterns structure. The contact plug includes a lower portion and a middle portion over the lower portion. A width of the middle portion is less than a width of the lower portion. The gate electrodes are surrounding a sidewall of the semiconductor stack. The air gap structures are disposed at outer sides of the plurality of gate electrode respectively.