The course contents are useful for understanding of microwave solid state devices and there applications. The development of semiconductor technology help us to fabricate low cost, low voltage operation and miniaturized solid state source. The Solid state devices are advantageous as longer life, require low voltage, easy control of amplitude of the transmitted waveform, wider bandwidths, low production cost and easy to install. The solid state devices includes here are Tunnel Diode, Gunn Diode, Read Diode, IMPATT Diode, BARITT Diode, TRAPATT Diode, Varactor Diode, etc. Theses solid state devices are widely used in microwave system for generation, amplification, or detection of microwave signal. These devices are compact and integrated in a printed circuit board. They are suffering from major drawback of low efficiency above 10GHZ, high noise, small tuning range, and more dependence of frequency on temperature. Solid state devices are categorised based on electrical characteristics such as nonlinear resistance type, nonlinear reactance type, negative resistance type, controllable impedance type. Solid state device can be categorised based on point contact diode, Schottky barrier diode, metal oxide semiconductor devices and metal insulator devices. Scientist have made numerous effort to design two terminal device. A tunnel diode is basically two terminal device, forward biased, heavily doped p-n junction diode. The transferred electron devices and avalanche transit time device developed, they can work at negative resistance region.