Let us imagine that we have a piece of a material with a controllable resistance, i.e., it can be near zero as a a conductor or a metal wire, or can it be near infinity, as the isolators, a semiconductor is that, a material which resistance can be changed either to grow or to decrease depending on the controlling variable, e.g., current or voltage or even charge, this make them -the ability to control in situ their resistance- adequate to IC integration, becuae using control signal one can made many features such as amplifying, switching, etc....