Most of the layers that are inside a device are fabricated by CVD (chemical vapour deposition).

The main difference for CVD processes (compared to PVD), is that chemical reactions take place in the chamber, and one of the products of the reactions is the deposited film. The precursors are usually gases, but it is possible to use also liquids. There are several types of CVD, depending on the pressure in the chamber, if plasma is used or not, etc.