Embodiments of the invention provide a semiconductor device having dielectric material and its method of manufacture. A manufacturing method comprises forming a layer of silicon over a substrate, forming an opening through the layer of silicon, filling the opening with a conductor; and anodically etching the layer of silicon so as to form porous silicon. Embodiments may further include passivating the porous silicon such as by treating its surface with an organometallic compound. Other embodiments of the invention provide a semiconductor device comprising a layer comprising functional devices; and an interconnect structure over the layer, wherein the interconnect structure comprises a porous silicon dielectric. In an embodiment of the invention, the interconnect structure comprises a dual damascene interconnect structure. Other embodiments may include a passivation step after the step of oxidizing the porous silicon.