Traditional terahertz amplifiers are highly dependent on compound semiconductor processes such as InP, which suffer from high costs and limited integration ability. In contrast, CMOS processes offer advantages in low cost and high integration. However, they face multiple challenges in the terahertz band, resulting in a scarcity of reported high-performance CMOS terahertz amplifiers. To break through the bottleneck of terahertz chip design in CMOS processes, this paper proposes a terahertz amplifier architecture based on the periodic stabilization technique. This technique enhances the gain at high frequencies while moving the input impedance of each stage into the stable region of the preceding stage at lower frequencies. It also absorbs unavoidable conductor losses into the stabilization network, effectively boosting the overall system gain performance and guaranteeing the overall stability. Multiple amplifier variants were fabricated in a 28-nm CMOS process. AMP1 achieves a peak gain of 18 dB at 300 GHz with a 3-dB gain bandwidth of 289–301 GHz. Compared with reported CMOS amplifiers, this work demonstrates a state-of-the-art operating frequency in 28-nm CMOS.