Metal oxide Semiconductor (MOS) materials based gas sensors have been developed in variety of applications such as industrial emission control, civil life, medical diagnosis, and environmental monitoring, due to their irreplaceable advantageous features, such as high sensitivity, small physical size, low cost and simplicity in fabrication. In addition to the material characteristics, heterojunction, based on a unique sensing mechanism, has already been proved to result in the improvement of the sensing performances compared to their single-component semiconductor gas sensors due to the synergetic effect from different sensing materials in the hetero-structure and the heterojunction barrier formed at the interfaces. In this talk, our recent progress on the synthesis of porous MOS heterostructures with nanostructured heterojunction in the thin film, nanowires and 2D nanomaterials will be presented. For example, highly-uniform bilayer and multilayer porous thin films were successfully fabricated using self-assembled soft template and simple sputtering deposition technique. The sensor based on the In₂O₃/CuO bilayer porous thin film shows obviously improved sensing performance to ethanol at the lower working temperature, compared to single layer counterpart sensors. The sensing mechanism based on p-n hetero-junction, which contributed to the enhanced sensing performance was also experimentally confirmed by a control experiment which the SiO₂ insulation layer was inserted between the In₂O₃ and CuO layers to break the p-n junction. Besides, in this talk I would like to briefly report the progress of the electronic noise based on carbon nanostructures assembled in smart cell phone.