a high - voltage transistor includes an active region including a diffused region of a first conductivity type defined by inner edges of a border of shallow trench isolation . a gate having side edges and end edges is disposed over the active region . spaced apart source and drain regions of a second conductivity type opposite the first conductivity type are disposed in the active region outwardly with respect to the side edges of the gate . lightly - doped regions of the second conductivity type more lightly - doped than the source and drain regions surround the source and drain regions and extend inwardly between the source and drain regions towards the gate to define a channel , and outwardly towards all of the inner edges of the shallow trench isolation . outer edges of the lightly - doped region from at least the drain region are spaced apart from the inner edges of the shallow trench isolation .