ABSTRACT
When electrical circuits are built, the physical environment consists of conductors separated from each other by insulating materials. Depending on the application, the properties of the insulating materials are chosen to satisfy requirements of low conductivity, a high or low dielectric permittivity and desirable loss properties. In most cases the high field properties of the materials do not play a role (certainly not in signal processing applications). This is also true with respect to electrical breakdown. However, there are exceptions. For instance, in transmitters the fields can be very large and the choice of insulators has to reflect those conditions. In semiconductor devices, dielectric breakdown of insulating layers can be a problem, but in many cases it is actually tunneling through the dielectric that is responsible for charge transport. In DRAM, the leakage currents in the memory storage capacitor have to be small enough to give a charge half-life of about one second over the full temperature range. In Flash memories, the charge is transferred via tunneling to the controlling site in the FET where it must then remain resident for years. This requires a really good insulator.
