Silicon is a nearly perfect material for making semiconductors. Intrinsically, a near insulator, but with minor doing, can become p-type or n-type. The only other material that comes close is germanium, but it has temperature issues. GaAs and InP are good for niche applications, but have limited utility for general purpose devices
Electron and hole mobilities high enough to get decent gains in transistors.
Can be made nearly defect-free for high yield.
Has a native and easily augmented native oxide that's nearly a perfect insulator
Has oxide that can be tunneled through for robust non-volatile storage
Can be fabricated into wafers over 12" in diameter for batch processing.
Has a near-ideal bandgap for reasonabl device thresholds and crystal structure that can handle low and high voltages.
Silicon is used for 2 reasons...
1)Cheap as sand on a beach...germanium and Gallium Arsnide are expensive materials to start with and less developed technologically.
2)Silicon "naturally" grows Silicon Dioxide Si02, which is the material required to make the gates/gate capacitors. All materials require impurity implant to make them p-type or n-type, after doing such, the gate needs to be made for the Source to Drain connections. Silicon gate capacitors are made by heating the wafer up and growing Si02, in any other material process a physical layer needs be applied which takes much more $. This is the main reason for Si wafers...on average this is 1/4-1/10 the cost of other technologies...
Hope this helps!