On the basis of investigations regarding the electrostatic discharge (ESD) sensitivity of GaAs microwave devices, we found that there is a need for protection circuits to prevent ESD degradation or destruction of microwave semiconductor devices and circuits. Since such protection circuits are not yet available for these frequency ranges, we developed a suitable protection concept. The field emission effect showed the qualities needed, and we developed metal and GaAs field emitters to fabricate very fast switches with the ability to handle very high current densities in order to obtain such protection circuits suitable for operation in the microwave frequency range.