Patent ID: 7960786
Filing Date: 2011-06-14
Classification: H01L

Abstract:
1. A semiconductor structure comprising: a semiconductor substrate of a first conductivity type; a pre-high-voltage well (pre-HVW) in the semiconductor substrate, wherein the pre-HVW is of a second conductivity type opposite the first conductivity type; a high-voltage well (HVW) over the pre-HVW, wherein the HVW is of the second conductivity type; a field ring of the first conductivity type occupying a top portion of the HVW, wherein at least one of the pre-HVW, the HVW, and the field ring comprises at least two tunnels of a same conductivity type as the respective pre-HVW, the HVW, and the field ring, and wherein the tunnels have a lower impurity concentration than the respective one of the pre-HVW, the HVW, and the field ring; an insulation region over the field ring and a portion of the HVW; a drain region in the HVW and adjacent the insulation region; a gate electrode over a portion of the insulation region; and a source region on an opposite side of the gate electrode than the drain region.