This paper reports on the design and experimental verifications of a passive step-up rectifier for MEMS piezoelectric energy scavengers. The purpose of the proposed circuit is to improve system startup for vibration micro-generators without the need of an external source of energy. The design chosen is based on a voltage multiplier where conventional diodes are replaced by PMOS low-VT transistors. The circuit is produced in 1.8V 0.18μm UMC CMOS technology. Test and verifications were performed using a real piezo scavenger providing an AC voltage of 0 to 350mVpeak at a frequency of around 2.4 kHz. Up to 2V DC was measured at the output of the rectifier.