This paper presents results of digital CMOS design for ultra-low power filter that uses logic cells operating at near-threshold voltage supplies. The cells were designed in 65 nm CMOS technology for ultra-low power. The hardware implementation of a pole-radius-varying Infinite Impulse Response (IIR) notch filter is addressed. Previous works have shown that digital design of pole-radius-varying (or Q factor-varying) IIR notch filters can suppress the transient effect. The proposed filter is synthesized using our custom 65 nm near-threshold voltage standard cells library. Comparisons from near-threshold operation to nominal voltages show large gains in energy-savings for this filter that make the logic architecture suitable for sub-nano-Joule per sample applications.