The "Twelfth International Conference on Simulation of Semiconductor Processes and Devices" (SISPAD 2007) continues a long series of conferences and is held in September 2007 at the TU Wien, Vienna, Austria. The conference is the leading forum for Technology Computer-Aided Design (TCAD) held alternatingly in the United States, Japan, and Europe. The first SISPAD conference took place in Tokyo in 1996 as the successor to three preceding conferences NUPAD, VPAD, and SISDEP. With its longstanding history SISPAD provides a world-wide forum for the presenta- tion and discussion of outstanding recent advances and developments in the field of numerical process and device simulation. Driven by the ongoing miniaturization in semiconductor fabrication technology, the variety of topics discussed at this meeting reflects the ever-growing complexity of the subject. Apart from the classic topics like process, device, and interconnect simulation, mesh generation, a broad spec- trum of numerical issues, and compact modeling, new simulation approaches like atomistic and first-principles methods have emerged as important fields of research and are currently making their way into standard TCAD suites.