Patent ID: 7144781

Claim:
A method of manufacturing a semiconductor device having a source region of a second conductivity type and a drain region of the second conductivity type that are surface layers of a semiconductor substrate of a first conductivity type, the drain region and source region extending in parallel in a first direction, and a drain drift region of the second conductivity type located between the source region and the drain region and separated from the source region in a second direction perpendicular to the first direction, the method comprising the steps of: forming a plurality of trenches in the semiconductor substrate in the first direction in parallel with the source region and the drain region, each of the trenches being such that a length thereof in the first direction is shorter than a length thereof in the second direction that; and through each of the trenches, implanting impurity ions into only first regions and a second region of the semiconductor substrate, the first regions being adjacent to side faces that are parallel with the first direction among side faces of each of the trenches, the second region being adjacent to a bottom face of each of the trenches, including implanting the impurity ions into the first regions without implanting into the second region by applying the impurity ions in planes perpendicular to the second direction, in directions that are oblique with respect to the respective side faces parallel with the first direction, and implanting impurity ions into the second region by applying the impurity ions perpendicularly to the bottom face.