Semiconductor, normally refers to a material which conductivity is between conductor and insulator. Semiconductor is a material which conductivity can be controlled from insulator to conductor. Semiconductors are of great importance in terms of both science and technology and economic development. Most of today's electronic products, such as computers, mobile phones or digital recorders, mostly have a very close relationship with semiconductors. Semiconductor materials are silicon, gallium arsenide and so on, the silicon is one of the most influential semiconductor materials in commercial applications.

      Semiconductor materials can be divided into elemental semiconductors and compound semiconductors according to chemical composition. Germanium and silicon are the most commonly used element semiconductors. Compound semiconductors include the third and fifth categories of compounds (gallium arsenide, gallium phosphide, etc.), the second and sixth categories of compounds (nickel sulfide, zinc sulfide, etc.), oxides (oxides of manganese, iron, copper), and solid solutions (gallium, aluminum, arsenic, phosphorus, etc.), also the combination of  three - five categories of compounds and two - six categories of compounds. In addition to the above crystalline semiconductors, there are amorphous glass semiconductors, organic semiconductors and so on.

       Semiconductors can be classified into integrated circuit devices, discrete devices, photoelectric semiconductors. And logic IC, analog IC, memory and other categories according to the manufacturing technology. These can also be classified into small categories. In addition, It can be classified according to the application fields and design methods. Although not commonly used, also can be classified according to IC, LSI, VLSI related to the scale. In addition, according to the signal processed, it can be divided into analog, digital, analog-digital mixing and function classification methods.