Patent ID: 8642370

Claim:
A process of forming a microelectronic mechanical system (MEMS) device, comprising the steps of: forming an overlying dielectric layer stack over a substrate, said overlying dielectric layer stack having an etch-resistant lower portion and an etchable sublayer; forming an access hole in said overlying dielectric layer stack through at least said etchable sublayer such that a surface of said etchable sublayer is exposed; covering said exposed surface of said etchable sublayer; and after covering said exposed surface of said etchable sublayer, etching a cavity in said substrate through said access hole, such that said cavity underlaps said overlying dielectric layer stack by at least 5 microns; wherein: an input/output (I/O) pad is disposed in said overlying dielectric layer stack under said etchable sublayer; said step of forming said access hole exposes said I/O pad so as to form an I/O opening.