Adding functionality to a passive Si interposer used in 2.5/3D integration, can result in system cost reductions. In this work, active components (diodes, BJT, ...) have been integrated on Si interposer using a new low-mask process flow. This low-cost process enables: (1) to move part of the area hungry ESD protection from the stacked dies to the interposer; (2) the realization of pre-bond testable interposers (DFT); and (3) components for analog circuits (diodes, npn, SCR, resistor).