Highly integrated and miniaturized neural sensing microsystems that provide stable observation, small form factor and biocompatible properties are crucial for brain function investigation and neural prostheses realization for capturing accurate signals from an untethered subject in his natural habitat [1, 2]. Such biomedical devices usually comprise sensors and CMOS circuits for biopotential acquisition, signal conditioning, processing and transmission. Many approaches have been reported, including stacked multichip [3, 4], microsystem with separated neural sensors  and monolithic packaged microsystem . Regardless of the integration schemes, the collected weak signals from the sensor need to pass through a string of interconnections including wire bonding, flip-chip bonding and welding or soldering bonds to the processing circuits. The excessive interfaces and connections introduce noise and lead to bulky packaged systems.