  We report in this paper the design, fabrication and experimental
characterization of a piezoelectric MEMS microgenerator. This device scavenges
the energy of ambient mechanical vibrations characterized by frequencies in the
range of 1 kHz. This component is made with Aluminum Nitride thin film
deposited with a CMOS compatible process. Moreover we analyze two possible
solutions for the signal rectification: a discrete doubler-rectifier and a full
custom power management circuit. The ASIC developed for this application takes
advantage of diodes with very low threshold voltage and therefore allows the
conversion of extremely low input voltages corresponding to very weak input
accelerations. The volume of the proposed generator is inferior to 1mm3 and the
generated powers are in the range of 1$\mu$W. This system is intended to supply
power to autonomous wireless sensor nodes.
