A compact and fabrication friendly polarization demultiplexer(P-DEMUX)is proposed and characterized to en-able wavelength-division-multiplexing and polarization-division-multiplexing simultaneously.The proposed structure is composed of a polarization-selective microring resonator in ultrathin waveguide and two bus channels in the silicon nitride-silica-silicon horizontal slot waveguides.In the slot waveguide,the transverse electric(TE)mode propagates through the silicon layer,while the transverse magnetic(TM)mode is confined in the slot region.In the designed ultra-thin waveg-uide,the TM mode is cut-off.The effective indexes of the TE modes for ultrathin and slot waveguides have comparable values.Thanks for these distinguishing features,the input TE mode can be efficiently filtered through the ultra-thin mi-croring at the resonant wavelength,while the TM mode can directly output from the through port.Simulation results show that the extinction ratio of the proposed P-DEMUX for TE and TM modes are 33.21 dB and 24.97 dB,and the insertion losses are 0.346 dB and 0.324 dB,respectively,at the wavelength of 1551.64 nm.Furthermore,the device shows a broad bandwidth(＞100 nm)for an extinction ratio(ER)of＞20 dB.In addition,the proposed P-DEMUX also has a good fabrication tolerance for the waveguide width variation of-20 nm≤Δwg≤20 nm and the microring width variation of-20 nm≤Δwr≤20 nm for a low insertion loss of＜0.75 dB and low ER of＜-18 dB.