We present a micro/nano-machining process to introduce nanostructured poly-silicon layer on the gate region of the pH-sensitive field effect transistors. Decoration of the gate of the field effect transistors by nanostructures plays an important role to improve the sensitivity of the pH-sensitive FETs. Electron beam lithography was exploited to realize the poly-Si nanopillars on the gate surface. Comparison between different micro and nanostructures demonstrates the potential of nanopillars to

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... e utilized on the gate of this device rather than micro-conical structures (different size and shapes) and vertically carbon nanotubes. A high sensitivity of 500 mV/pH has been achieved, through the incorporation of silicon based nanopillars.