title: Front end of line
text: # 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.) are patterned in the semiconductor. FEOL generally covers everything up to (but not including) the deposition of metal interconnect layers.
  
  For the CMOS process, FEOL contains all fabrication steps needed to form isolated CMOS elements:
  
  * Selecting the type of wafer to be used; Chemical-mechanical planarization and cleaning of the wafer.
  * Shallow trench isolation (STI) (or LOCOS in early processes, with feature size > 0.25 μm)
  * Well formation
  * Gate module formation
  * Source and drain module formation
  