Abstract: A semiconductor device comprises a monocrystalline silicon wafer having a major surface lying in the {100} crystal plane. Disposed on the surface is a mesa having a generally square cross-section with generally rounded corners. The mesa has four main side walls each having a slope of around 45 degrees with respect to the base plane of the mesa, and the horizontal edges of the main side walls are disposed at an angle of at least around 12 degrees to the {111} directions on the wafer surface. The corners of the mesa each comprises a number of surfaces also having slopes of around 45 degrees and one surface having a slope of around 54 degrees. A high-low (N.sup.+ N.sup.- or P.sup.+ P.sup.-) junction is disposed within the mesa and makes a continuous line intercept with the mesa side walls around the entire periphery of the mesa. Except for exceptionally small deviations of no great significance, the high-low junction intercept is at a constant height location entirely around the mesa periphery.

Abstract: A semiconductor rectifier device includes a mesa structure formed on a surface of a monocrystalline silicon wafer, the mesa having four side walls meeting at rounded corner walls. The slope of the mesa side walls is 45 degrees and the slope of each corner wall varies between 45 and 54 degrees. The mesa is fabricated by providing a square etchant mask having rounded corners on a <100> crystal plane of a silicon wafer with the straight sides of the mask disposed at an angle of 45 degrees with <111> directions on the wafer surface. The mask corners are symmetrical and comprise, from a mid point of the corners, oppositely extending short straight lines forming an angle of 150 degrees or less therebetween. The rear end of each short line is connected by a series of end to end straight lines angled relative to one another to form a generally smooth line merging with straight sides of the mask.