A surface-micromachined high-extinction-ratio polarizing beam splitter (PBS) using low absorptive silicon nitride layers for blue wavelength applications are demonstrated. The micro polarizing beam splitter consists of novel stack of two silicon nitride layers separated by an air gap. A PBS optimization model is established to achieve both high extinction-ratio and adequate process margin. The polarization extinction ratios of 25 dB for the reflected light and 15 dB for the transmitted light were experimentally achieved at λ=405 nm. The fabrication of the PBS is compatible with other micro diffractive elements to build a micro optical bench, thus, feasible for short wavelength optical storage applications.