The synchrotron radiation (SR) stimulated etching of silicon elastomer polydimethylsiloxane (PDMS) using XeF(2) as an etching gas has been demonstrated. An etching system with differential pumps and two parabolic focusing mirrors was constructed to perform the etching. The PDMS was found to be effectively etched by the SR irradiation under the XeF(2) gas flow, and the etching process was area-selective and anisotropic. An extremely high etching rate of 40-50 microm (10 min)(-1) was easily obtained at an XeF(2) gas pressure of 0.2-0.4 torr. This suggests that SR etching using XeF(2) gas provides a new microfabrication technology for thick PDMS membranes, which can open new applications such as the formation of three-dimensional microfluidic circuits.