The general topic of MEMS modeling is a vast and nontrivial one  due to the great variety of physical behavior encountered in MEMS devices. The field can be narrowed down, however, when we focus on MEMS devices for RF/microwave applications. In these cases, the great majority of devices of interest fall into one of two categories: the micromachined motionless 3-D structure, or the electrostatically actuated structure. In these contexts, then, one can posit two modeling methodologies: first principles numerical models, and reduced-order analytical (lumped-element) models.
Within the former category, one finds that there exist mature, independently developed modeling tools addressing, on the one hand, the electromechanical behavior of devices (e.g., ANSYS, ABAQUS, Intellisense, CoventorWare), and on the other hand, their electromagnetic behavior (e.g., Ansoft Maxwell, Agilent HFSS). Under these circumstances (i.e., without an allencompassing single modeling tool), RF MEMS modeling may be predicated as shown in Figure 3.41.