The present application discloses a semiconductor device and a method for fabricating the semiconductor device. The semiconductor device includes a substrate; an isolation layer positioned in the substrate and defining an active area of the substrate, wherein the active area includes a transistor portion and a programmable portion extending from the transistor portion; a buried gate structure positioned in the transistor portion; a drain region positioned in the programmable portion and the transistor portion, and adjacent to the gate structure; a source region positioned in the transistor portion, adjacent to the gate structure, and opposite to the drain region with the buried gate structure interposed therebetween; a middle insulating layer positioned on the programmable portion; and an upper conductive layer positioned on the middle insulating layer. The drain region in the programmable portion, the middle insulating layer, and the upper conductive layer together configure a programmable structure.