High aspect ratio silicon was fabricated by metal-assisted chemical etching (MACE). We have fabricated zone plate with 16 nm outermost zone width and 8 μm thickness, thus achieving a very high aspect ratio up to 500. Such zone plates have the potential for high efficiency and fine spatial resolution for x-ray nanofocusing applications. High aspect ratio diamond was fabricated by reactive ion etching (RIE). We have fabricated diamond gratings with 300 nm half-pitch and more than 10 μm thickness. Diamond has more thermal conductivity than silicon. Such gratings could be used as x-ray beam splitter for free-electron laser.