Recessed trench MOSFET process without critical alignments makes very high densities possible

Trench MOSFETs have opened the way to extremely high-density devices with correspondingly lower on-resistances. However, in practice, it has proved difficult to fully exploit this structure because fabrication requires critical submicron alignments between the various layers. A new recessed gate structure that requires no critical alignments within the active area is presented for the first time. Whilst simplifying the manufacturing procedure, this also opens the way for higher density trench MOSFETs with even lower on-resistances.