Bit Tech published a 4-page article that covers all the steps involved in the production of a CPU, you can read it over here.
Amazingly, after oxygen, silicon is the most plentiful element in the earth’s crust. It’s not just lying around in electronics-grade lumps though, and needs to be extracted from sand, where it resides in the form of silicon dioxide (SiO2).
Once the silicon has been purified to the required degree (something in the region of 99.9999999 per cent pure), it's formed into a single contiguous 100kg ingot of silicon. The ingot can then be sliced into individual 1mm thick disks, called wafers, which should be recognizable to most tech junkies.