Several materials are commonly used in integrated circuits. These materials are mainly silicon, and silicon dioxide. Other materials of interest are mold compound, and FR4 epoxy as they are in the immediate environment of ICs.
Silicon is the most widely used material inside ICs. All components but true capacitors are built from silicon.
In semiconductors, two types of carriers exist.
Silicon oxide is probably the most used material after silicon in ICs. Capacitors are built from metal and oxide and the dielectric layers between connection layers are made from oxide.
Silicon nitride is used as a passivation layer over the metal stack and final oxide.
Mold compound is the material surrounding silicon in molded plastic packaged ICs.
PCBs, often made from FR4 material are the ICs environment outside the package.