Semiconductors are materials which conduct electricity to an extent somewhere between that of a conductive material (copper, iron) and an insulating material (cork, rubber). Any person with any knowledge of semiconductors will know that they are at the heart of modern technology, in computers, phones and a wide range of electronic devices. Their chemical attributes are discussed in detail below.
A key distinction is that semiconductors are materials which conduct electricity via electron flow rather than ionic conduction
Although semiconductors can take liquid form, a majority of semiconductors are crystalline solids, according to Howstuffworks.com. Silicon is used to create most commerically-applied semiconductors for the manufacture of electronic chips and things of that nature. Silicon appears with a lot of metallic elements on the periodic table, but is not a metal, although its crystals can look metallic in nature to the untrained eye.
A key chemical property of pure semiconductor materials is that their conductivity can be modified by a process commonly known as doping. By introducing quantities of other compounds into the crystalline lattice of a pure semiconductor, the material's conductivity can be raised or lowered as required. The introduction of these compounds obviously alters the chemical attributes of the semiconductive material. Phosphorous or arsenic are added to silicon in small quantities for N-type doping, while borum or gallium is used for P-type doping, both transforming a standard silicon crystal from an insulator into a mid-range conductor.
So, most commonly used semiconductors are silicates, and most are crystalline and solid. Although there are some liquid semiconductors, it's important to remember the distinction between a semiconductor, which conducts electricity through electron flow, and an electrolyte, which uses ionic conductivity to pass current between two electrodes.
Semiconductors tend to be very pure materials, the above-mentioned doping compounds notwithstanding. This is because even trace impurities can have an adverse affect on their conductivity. Their crystalline structure also needs to be as close to perfect as possible in order to maintain their conductivity to the extents required by their function.
In conclusion, although there is a significant variety of materials which can be used for semiconductors, most will be silicon-based, and may use either N-type or P-type doping to reach the required level of conductivity. In addition to being silicon-based, most semiconductors will also be crystal lattices, in order to facilitate the electron flow through the solid substance.
Semiconductors are at the heart of many electronic components, and so new semiconductor materials are being researched all the time, each with new chemical attributes. The above are broad guidelines only.