The epitaxial layer transfer process was previously introduced to integrate high-quality and ultrathin III-V compound semiconductor layers on any substrate. However, this technique has limitation for fabrication of sub-micron nanoribbons due to the diffraction limit of photolithography. In order to overcome this limitation and scale down its width to sub-50 nm, we need either a costly short wavelength lithography system or a non-optical patterning method. In this work, high-quality III-V compound semiconductor nanowires were fabricated and integrated onto a Si/SiO2 substrate by a soft-lithography top-down approach and an epitaxial layer transfer process, using MBE-grown ultrathin InAs as a source wafer. The width of the InAs nanowires was controlled using solvent-assisted nanoscale embossing (SANE), descumming, and etching processes. By optimizing these processes, NWs with a width less than 50 nm were readily obtained. The InAs NWFETs prepared by our method demonstrate peak electron mobility of ~1600 cm2/Vs, indicating negligible material degradation during the SANE process.