The present application discloses a semiconductor device and a method for fabricating the semiconductor device. The semiconductor device includes a first semiconductor structure and a first connecting structure, wherein the first connecting structure includes a first connecting insulating layer positioned on the first semiconductor structure, two first conductive layers positioned in the first connecting insulating layer, and a first porous layer positioned between the two first conductive layers. A porosity of the first porous layer is between about 25% and about 100%.