3D integration and wafer level packaging (WLP) with through-silicon vias offer benefits like reduced footprint and improved performance. CMOS imaging sensors is one of the first successful introductions of a product with TSVs on the market, and 3D integrated memory stacks are expected to follow soon. Also sensor and actuator systems based on micro- and nano-electromechanical systems (MEMS/NEMS) will greatly benefit from WLP and 3D integration of the transducers and their readout and controller ICs. Ultimately, heterogeneous integration of different device technologies will allow the fabrication of MEMS/IC and NEMS/IC products with new and improved functionalities. For this to become a reality, cost-effective and reliable 3D integration technologies need to be developed. This paper gives an overview and reports on the current status of 3D interconnect technologies that will enable 3D integration for advanced MEMS/NEMS applications.