a polysilicon resistor fuse has an elongated bow - tie body that is wider at the opposite ends relative to a narrow central portion . the opposite ends of the body of the fuse have high concentrations of n - type dopants to make them low resistance contacts . the upper portion of the central body has a graded concentration of n - type dopants that decreases in a direction from the top surface toward the middle of the body between the opposite surfaces . the lower central portion of the body is lightly doped with p - type dopants . the central n - type region is a resistive region .