Front end of line

The front end of line (FEOL) is the first portion of IC fabrication where the individual components (transistors, capacitors, resistors, etc.)

[1] FEOL generally covers everything up to (but not including) the deposition of metal interconnect layers.

[2] For the CMOS process, FEOL contains all fabrication steps needed to form isolated CMOS elements:[3][4] Finally, the surface is treated to prepare the contacts for the subsequent metallization.

This concludes the FEOL process, that is, all devices have been built.

BEOL is thus the second portion of IC fabrication where the individual devices are connected.

Illustration of FEOL (device generation in the silicon, bottom) and BEOL (depositing metalization layers, middle part) to connect the devices.
CMOS fabrication process