A method for fabricating a semiconductor device includes preparing a lower structure including an interconnection, forming a first contact plug coupled to the interconnection, and forming an alternating stack of dielectric layers and sacrificial layers over the first contact plug and the lower structure. The method further includes forming an opening that penetrates the alternating stack and exposes the first contact plug, forming a sacrificial plug including a void in the opening, forming a contact hole that exposes the first contact plug by etching a portion of the sacrificial plug, and forming a second contact plug in the contact hole.