High performance $Si_{0.8}Ge_{0.2}$ heterostructure metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated using well-controlled delta-doping of boron and $Si_{0.8}Ge_{0.2}$/Si heterostructure epitaxal layers grown by reduced pressure chemical vapor deposition. In this paper, we report 1/f noise characteristics of the SiGe pMOSFETs measured under various bias conditions of the gate and drain voltages changing in linear operation regions. From the noise spectral density, we found that the gate and drain voltage dependence of the noise represented same features, as usually scaled with $f^{-1}$ However, 1/f noise was found to be much lower in the device with boron delta-doped layer, by a factor of $10^{-1}_10^{-2}$ in comparison with the device fabricated without delta-doped layer. 1/f noise property of delta-doped device looks important because the device may replace bipolar transistors most commonly embedded in high-frequency oscillator circuits.