This thesis work was carried out at PoliFAB and deals with the design and the fabrication of a frequency-modulated magnetometer combining silicon MEMS and magnetic elements. The sensor constitutes a proof of concept device for the European FET Open project OXiNEMS (OXide NanoElectroMechanical Systems), which aims to realize a new generation of ultra-sensitive magnetometers integrating transition metal oxides M/NEMS and superconductive or ferromagnetic materials. These novel hybrid sensors are expected to overcome the limitations of the magnetometers employed nowadays in magnetoencephalographic (MEG) systems (e.g. SQUIDs), hence paving the way for novel diagnostic methods, such as the combined MEG/ULF-MRI (ultra-low field magnetic resonance imaging) technique.