formed has a phosphorus concentration of 3 9 wt and a boron concentration of 2 7 wt and is about 5000 u00e5 in thickness in this case the phosphorus and boron concentrations are the averages of the measured values for 100 wafers measured at 500 points measurements were made on each wafer at the central point and the other four points lying on the straight lines that intersect at right angles at the central point and being about 21 mm away from the perimeter of wafer 8 the variation in phosphorus concentration ranges from 3 8 wt to 4 7 wt the variation in boron concentration ranges from 2 8 wt to 3 5 wt the variation in the thickness of the boron containing film is u00b1 4 9 in the surface of a piece of semiconductor wafer 8 and 2 6 among semiconductor wafers 8 the variation in the film thickness between different batches each batch consisting of 100 wafers is less than 0 04 the film thickness was measured at five points including the center of each semiconductor wafer 8 just as in the concentration measurements described above the four points other than the center were at the points 10 mm away from the.