The terahertz (THz) frequency range (0.3–3 THz) , has garnered extensive attention in recent years. THz detectors are fundamental components in terahertz wave technology research. By virtue of its advantages of low cost, high yield, and easy integration, CMOS technology is emerging as an alternative to other technologies. To address the performance degradation of the terahertz detector due to low radiation efficiency, a patch antenna with upward radiation is employed, characterizing its various performance attributes. The architecture of the proposed THz detector is shown in Fig.1. The detector consists of an on-chip patch antenna and a source-feeding NMOS transistor. To enhance the efficiency of terahertz power transmission between the antenna and the transistor, an impedance matching network is integrated. This network consists of a single microstrip transmission line with a length of 105 μm. Additionally, a notch filter is designed at the transistor gate to minimize the impact of the gate bias line and chip bonding wires on impedance matching. The notch filter is implemented as an open-circuited microstrip transmission line with a length of 124 μm and a width of 1 μm, fabricated from the top metal layer, while the bottom metal layer serves as the ground plane. Simulation results indicate that incorporating an impedance matching network enhances the detector's performance by approximately 20 times compared to the configuration without the impedance matching network. The detector is fabricated in the 180 nm CMOS process, with an area of 460 μm×497 μm. Measurement results, as shown in Fig.10, demonstrate that the detector operates over a frequency range of 220-325 GHz, with a maximum responsivity (R_v) of 1 524 V/W at 281 GHz and a minimum noise equivalent power (NEP) of 19.9 pW/Hz^1/2 when V_g = 0.48 V. Table 1 presents a performance comparison between the detector designed in this work and other previously reported detectors. Compared to detectors that require integrated silicon lenses, the patch antenna in the proposed design radiates upwards, thereby avoiding the transmission of terahertz waves through a lossy substrate and eliminating the need for expensive high-resistivity silicon lenses to enhance antenna radiation efficiency. Furthermore, compared to detectors that do not integrate silicon lenses, the detector designed in this study exhibits a lower NEP. Utilizing this detector, a terahertz scanning imaging system was constructed, as depicted in Fig.12. A 281 GHz terahertz detector has been designed based on a 180 nm standard CMOS process. The detector comprises a patch antenna, an NMOS field-effect transistor, an impedance matching network, and a notch filter. It operates over a frequency range of 220-325 GHz, achieving a maximum R_v of 1524 V/W at 281 GHz and a minimum NEP of 19.9 pW/Hz^1/2. This performance is comparable to that of existing direct detectors which require integrated silicon lenses. A scanning imaging system has been constructed using this detector, and the detector can obtain clear scanned transmission images under continuous terahertz illumination.