There have been a number of disclosures related to building microphone elements on the surface of a silicon die.  Certain of these disclosures have come in connection with the hearing aid field for the purpose of reducing the size of the hearing aid unit.  While these disclosures have reduced the size of the hearing aid, they have not disclosed how to protect the transducer from outside interferences.  For instance, transducers of this type are fragile and susceptible to physical damage.  Furthermore, they must be protected from light and electromagnetic interferences.  Moreover, they require an acoustic pressure reference to function properly.  For these reasons, the silicon die must be shielded. 
Some shielding practices have been used to house these devices.  For instance, insulated metal cans or discs have been provided.  Additionally, DIPs and small outline integrated circuit (SOIC) packages have been utilized.  However, the drawbacks associated with manufacturing these housings, such as lead time, cost, and tooling, make these options undesirable.