Patent ID: 7288824

Claim:
A microelectromechanical device comprising: a chamber; a first layer; a first encapsulation layer comprising a permeable material, wherein first encapsulation layer forms at least a portion of a wall of the chamber; a micromechanical structure, wherein: (1) at least a portion of the micromechanical structure is formed in and/or from the first layer, and (2) at least a portion of the micromechanical structure is disposed in the chamber; a second encapsulation layer, disposed on the first encapsulation layer to seal the chamber, wherein the second encapsulation layer is a semiconductor material and wherein the first and second encapsulation layers are different from the first layer; and a field region disposed outside and above the chamber, wherein: the field region includes monocrystalline silicon; the first encapsulation layer is a semiconductor material; a first portion of the first encapsulation layer includes monocrystalline silicon and a second portion of the first encapsulation layer includes a porous or amorphous silicon; the second portion of the first encapsulation layer is a portion of the wall of the chamber; a portion of the second encapsulation layer that is on the second portion of the first encapsulation layer includes polycrystalline silicon.