In this paper, we demonstrate using extensive TCAD simulations that low frequency noise behavior is significantly different in presence of halo implants. The study of the noise behavior is extended to source side halo, drain side halo, symmetric halos and uniformly doped devices for different doping and length of the halo regions. Our study shows that source side halo region is responsible for the anomalous noise behavior in saturation. Such noise behavior can be accurately modeled with the presented SPICE model over wide range of biases and geometries. This study physically explains the trends observed in low frequency noise measurement in advanced CMOS technologies.