Hybrid integration of living cells and electronic circuits oil a chip requires a high-density matrix of sensors and actuators. This matrix must be processable oil top of CMOS devices and must be bio-compatible in order to support living cells. Recent studies have shown that the use of nail structures combined with a phagocytosis-like event of the cell can be exploited to improve the electrical coupling between a cell and a sensor. In this paper, two CMOS-compatible fabrication methods for sub-micron nails will be presented. The biocompatibility and proof-of-concept is demonstrated by the culturing of PC 12 neuroblastoma cells. Electrical functionality is shown by simultaneous stimulation and recording of pig cardiomyocyte cells. Biocompatibility aspects for more demanding cortical cell cultures have been addressed in a preliminary assessment. (c) 2007 Published by Elsevier Ltd.