Patent ID: 8207577

Claim:
A high voltage field-effect transistor (HVFET) comprising: a substrate of a first conductivity type; a first well region of a second conductivity type disposed within the substrate, the first well region having a lateral boundary; a drain region of the second conductivity type disposed within the first well region, the drain region having a first dimension in a first lateral direction, an extended drain region of the first well region separating the drain region from the lateral boundary in a second lateral direction orthogonal to the first lateral direction; a second well region of the first conductivity type disposed within the substrate adjacent to, and laterally extending into, the first well region, the second well region extending in the second lateral direction past the lateral boundary: a source region of the second conductivity type disposed in the second well region, a channel region being defined between the source region and the first well region; a field oxide layer that covers the first well region, the field oxide layer having a first thickness and extending in the second lateral direction from near the drain region to near the second well region in an active area of the HVFET; a gate oxide that covers the channel region in the active area, the gate oxide having a second thickness that is substantially thinner than the first thickness, the gate oxide having a substantially linear edge that extends in the first lateral direction, the substantially linear edge having a second dimension in the active area; a gate disposed over the channel region, the gate extending in the second lateral direction from the source region to over a portion of the field oxide layer, the gate being insulated from the channel region by the gate oxide in the active area, the gate extending in the first lateral dimension over an inactive area of the HVFET beyond the second dimension of the gate oxide, the gate being insulated from the first and second well regions over the inactive area solely by the field oxide layer.