Abstract: Zener diodes and other semiconductor junctions having very low noise characteristics and improved yield may be obtained by first ion implanting a suitable impurity into a substrate wafer, and then forming the p-n junction using a very rapid thermal activation and annealing process. For p-n junctions formed with boron (.sup.11 B) implanted into n-type silicon to a peak concentration exceeding 10.sup.20 atoms/cm.sup.3, the rapid activation process comprises heating from about room temperature to about 1150.degree. C. in 12-30 seconds, and then cooling back below 1000 degrees C. in less than 5 seconds. Noise voltages measured on devices formed using the invented process were typically much lower and more narrowly grouped than on devices of the prior art. Dynamic impedance was also slightly reduced.