Back end of line

The BEOL process deposits metalization layers on the silicion to interconnect the individual devices generated during FEOL (bottom).
CMOS fabrication process

Back end of the line or back end of line (BEOL) is a process in semiconductor device fabrication that consists of depositing metal interconnect layers onto a wafer already patterned with devices. It is the second part of IC fabrication, after front end of line (FEOL). In BEOL, the individual devices (transistors, capacitors, resistors, etc.) are connected to each other according to how the metal wiring is deposited.