This paper describes a simple method to predict the electrical impedance spectrum of single & cultured cells in micro-devices. It can be used for the rapid design of microsensors as well as for more fundamental studies about the interactions of electric fields with bio-cells. The finite element (FEMLAB) and the transport lattice (HSPICE) methods are coupled through the MATLAB environment for fast calculations of electrical impedance spectra (EIS). The impedances of simple test structures have been simulated and compared with their corresponding analytical solution. In the [10Hz-10GHz] frequency range, the maximum error was found to be lower than 6%. The geometry of our micro-device has been optimised with this method and the effects of various biological parameters have been analysed. This work has been performed in the framework of LIMMS, a joint laboratory between the CNRS (France) and the Institute of Industrial Science (University of Tokyo-Japan).