A semiconductor is a material with electrical conductivity between that of a conductor, like copper, gold and silver, and an insulator, such as glass and rubber.
They can be made from a lot of different materials, but some of the most commonly used ones are silicon, germanium and gallium arsenide, which is used in laser diodes, solar cells, microwave-frequency integrated circuits among other things.

Unlike metals, a semiconductors resistivity falls as its temperature rises.

Doping

A semiconductors properties can be altered in useful ways by introducing impurities into its crystal structure, also called doping.
When two differently doped regions exist in the same crystal a semiconduuctor junction is created.

Devices using semiconductors can have a range of useful properties, like passing current more easily in one direction than the other, showing variable resistance, sensitivity to light or heat.
Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion.

Edge Grinding

Silicon wafers have sharp edges after being cut and chip easily, thats why wafer edges gets ground down to remove sharp and brittle edges.
Edge shaping also makes the wafer perfectly round. The rounding is usually done with a profiled diamond wheel.