Si x N y/a-Si/Si x N y thin film RF-MEMS switches were fabricated by unconventional PECVD process using surface micromachining approach. The mechanical properties of tri-layer were measured by nanoindentation and wafer curvature method. Deflections of switches clamped on two opposite edges were measured by a profilometer applying increasing quasi-point pressure loads. Finite Element Analysis (FEA) was used to study the mechanical behavior of clamped-clamped switches. An analytical solution was developed and validated, numerically and experimentally, to describe the load-deflection response of perforated membranes to quasi-point loads. The proposed function was used to determine the internal stress of the investigated membranes; the relative error between the predicted and calculated stress values was in the range 2.1–8.5%.