Multiple optical elements utilize crossing of channel optical waveguides. This paper introduces efficient silicon wire waveguide crossing by means of vertical coupling of tapered Si wire with upper polymer wide strip waveguide through a silica buffer. Numerical simulations by 3D FDTD prove that optimal structure of 70 µm length can provide 98% efficiency for through pass and 99.9% efficiency for cross pass, as well as negligible back reflection (-50 dB) and cross talk (-70 dB). Proposed waveguide crossing on thin silicon-on-insulator CMOS compatible structures could find multiple applications in Photonics.