Question

How is zener diode fabricated so as to make it a special purpose diode?

Answer 1

a zener diode is special because it can even work in reversed biased condition without its breakdown

a zener diode consists of 2 components

firstly the diode itself in reversed biased condition and the second one is a load resistor connected in series

so in case if there is a fluctuation in voltage say excess voltage is there then zener diode passes the extra voltage towards load resistance it lets only the amount of voltage pass through it which it needs hence maintaining constant current for the device

hope this helps