One-dimensional nanostructures, such as nanowhisker, nanorod, nanowire, nanopillar, nanocone, nanotip, nanoneedle, have attracted significant attentions in the past decades owing to their numerous applications in electronics, photonics, energy conversion and storage, and interfacing with biomolecules and living cells. The manufacturing of nanostructured devices relies on either bottom-up approaches such as synthesis or growth process or top-down approaches such as lithography or etching process. Here we report a unique, synchronized, and simultaneous top-down and bottom-up nanofabrication approach called simultaneous plasma enhanced reactive ion synthesis and etching (SPERISE). For the first time the atomic addition and subtraction of nanomaterials are concurrently observed and precisely controlled in a single-step process permitting ultrahigh-throughput, lithography-less, wafer-scale, and room-temperature nanomanufacturing. Rapid low-cost manufacturing of high-density, high-uniformity, light-trapping nanocone arrays was demonstrated on single crystalline and polycrystalline silicon wafers, as well as amorphous silicon thin films. The proposed nanofabrication mechanisms also provide a general guideline to designing new SPERISE methods for other solid-state materials besides silicon.