A method and apparatus for providing a sub-ground plane for a micromachined device. The sub-ground plane is formed in or on the substrate. Above the sub-ground plane is a dielectric and then a discontinuous conductive layer used for interconnects for parts of the micromachined device. A movable microstructure is suspended above the interconnect layer. A conductive layer can be suspended above the movable microstructure. In one embodiment, the sub-ground plane is diffused into the substrate or a well in the substrate, and is of an opposite type from the type of silicon into which it is diffused. Alternatively, the sub-ground plane is formed from a conductive layer, deposited over the substrate before the layer used for interconnects.