The chips in the steps below are not part of the iPhone 4, but are included to illustrate the incredible structures of MEMS gyroscopes.

Shown in these photos is the ST LYPR540AH Tri-axis MEMS gyroscope, shot by a scanning electron microscope (SEM).

MEMS devices require extremely complicated and sensitive manufacturing procedures to produce the kind of accuracy needed for reliable sensors.

Most MEMS devices require a combination of deposition of a film layer, patterning to mask off areas of the deposited film to remain after etching, and etching to remove excess film to achieve the final product.