Fresnel zone plates (ZP's) are now widely used as imaging or focusing optical devices in soft x-ray region. They are fabricated by the semiconductor technology. Since the ideal spatial resolution is almost equal to the outermost zone width, the progress of ZP's completely depends on that of fabrication technology of the ultra-fine structures. The outermost zone width has recently reached 20-30nm. One of the popular applications of the ZP's is to the x-ray microscope. Along with the recent progress in synchrotron radiation sources and laboratory-size laser produced plasma x-ray sources, many x-ray microscopes are in operation or under construction in the world. In this paper, the optical property of ZP's and the present status of the applications are briefly described.
