We fabricated silicon nanowire fieldeff ect transistors that incorporate single-layers of parallel silicon nanowire channels via a combined bottom- up/top-down method. The channel material was epitaxially grown by the nanoparticle catalyzed vapor-liquid solid (VLS) method directly in the device structure to bridge the gap between adjacent short (~60 nm) silicon-on-insulator (SOI) entrenched side-walls The utilization of short SOI sidewalls allowed for the selective attachment of single layers of catalyst particles on the Si side-walls, and hence allowed for the growth of single layers of entrenched channel bridges. Moreover, we were able to modulate the charge density of the wires immediately after growth without post-processing by biasing the planar back-gate. The measured 3 terminal current-voltage data confirms the field-effect transistor behavior of the fabricated device. Moreoever, device simulation analysis predicts that the as-grown nanowires are moderately doped due to autodoping effects during the VLS growth process.