This article presents the development of single-nanometer magnetic tunnel junctions (MTJs) using a CoFeB/MgO multilayered structure, which allows for tailored performance for applications requiring high data retention or high-speed switching. The study addresses the challenges of scaling MTJs to smaller sizes while maintaining required data retention and switching speed. By engineering the number of CoFeB/MgO interfaces and the thickness of the CoFeB layer, the researchers demonstrate ultra-small MTJs with a diameter of 2.0 nm. These MTJs exhibit high data retention (over 10 years) and high-speed switching (10 ns or below) in sub-5-nm devices. The proposed stack design shows potential for high-performance and high-density spin-transfer torque magnetoresistive random access memory (STT-MRAM). The results highlight the effectiveness of emphasizing either shape anisotropy or interfacial anisotropy to achieve the desired performance for retention-critical and speed-critical applications, respectively.This article presents the development of single-nanometer magnetic tunnel junctions (MTJs) using a CoFeB/MgO multilayered structure, which allows for tailored performance for applications requiring high data retention or high-speed switching. The study addresses the challenges of scaling MTJs to smaller sizes while maintaining required data retention and switching speed. By engineering the number of CoFeB/MgO interfaces and the thickness of the CoFeB layer, the researchers demonstrate ultra-small MTJs with a diameter of 2.0 nm. These MTJs exhibit high data retention (over 10 years) and high-speed switching (10 ns or below) in sub-5-nm devices. The proposed stack design shows potential for high-performance and high-density spin-transfer torque magnetoresistive random access memory (STT-MRAM). The results highlight the effectiveness of emphasizing either shape anisotropy or interfacial anisotropy to achieve the desired performance for retention-critical and speed-critical applications, respectively.