To solve the problem of fast thermal and electrostatic simulation of microsystem elements two different field solver tools have been developed at TUB. The µSTHERMANAL program is capable for the fast steady state and dynamic simulation of suspended multilayered microsystem structures, while the 2D-SUNRED program is the first version of a general field solver program, based on an original method, the Successive Network Reduction. This program offers a very fast and accurate substitute of FEM programs for the solution of the Poisson equation, e.g. solving a 32000 grid problem in about 6 minutes on a 586 PC. Application examples show the usability of the tools.