A　broadband　and　CMOS-compatible　polarization　beam　splitter　and　rotator　(PSR)　built　on　the　silicon　nitride　-on-silicon　multilayer　platform　is　presented.　The　PSR　is　realized　by　cascading　a　polarization　beam　splitter　and　a　polarization　rotator,　which　are　both　subtly　constructed　with　an　asymmetrical　directional　coupler　waveguide　struc-ture.　The　advantage　of　this　device　is　that　the　function　of　PSR　can　be　directly　realized　in　the　SiN　layer,　providing　a　promising　solution　to　the　polarization　diversity　schemes　in　SiN　photonic　circuits.　The　chip　is　expected　to　have　high　power　handling　capability　as　the　light　is　input　from　the　SiN　waveguide.　The　use　of　silicon　dioxide　as　the　upper　cladding　of　the　device　ensures　its　compatibility　with　the　metal　back-end-of-line　process.　By　optimizing　the　struc-ture　parameters,　a　polarization　conversion　loss　lower　than　1　dB　and　cross　talk　larger　than　27.6　dB　can　be　obtained　for　TM-TE　mode　conversion　over　a　wavelength　range　of　1450　to　1600　nm.　For　TE　mode,　the　insertion　loss　is　lower　than　0.26　dB　and　cross　talk　is　larger　than　25.3　dB　over　the　same　wavelength　range.　The　proposed　device　has　good　potential　in　diversifying　the　functionalities　of　the　multilayer　photonic　chip　with　high　integration　density.(c)　2023　Optica　Publishing　Group