Ultralow specific on resistance UMOSFET with trench contacts for source and body regions realised by selfaligned process

An ultralow on resistance power UMOSFET having a refined contact structure has been fabricated by a selfaligned process. The most important feature of this UMOSFET is its great increment of channel width per unit area, which leads to a noticeable reduction in the on resistance. A 50 V UMOSFET with a specific on resistance of 0.58 m Omega cm² has been achieved despite employing a relatively thick (520 mu m) substrate with a resistivity of 8 m Omega cm.