The present disclosure provides to a semiconductor memory device. The semiconductor memory device includes a substrate having a cell area and a peripheral area; and a first bit line structure disposed on and protruding from a surface of the cell area. The first bit line structure is sandwiched by a pair of air gaps and a barrier layer is conformally overlaying the air gaps adjacent to the sidewalls of the first bit line structure and the cell area. The first bit line structure has a sidewall and an ascending top portion, and a landing pad is disposed over the ascending top portion and the sidewalls of the first bit line structure. The landing pad has an inclined surface corresponding to the ascending top portion of the first bit line structure.