Spin–orbit torque magnetic tunnel junctions (SOT-MTJs) with high tunneling magnetoresistance (TMR) ratio and high energy-efficiency are crucial for the development of SOT-magnetic random-access memory and other SOT devices. Here, the SOT-MTJs doped with an ultrathin layer of 0.2 nm CoFeB in the W writing line are fabricated, and the TMR ratio of the updated MTJs is up to 179%. Meanwhile, the SOT efficiency of the W layer doped with magnetic atoms (∼0.149) is weakly dependent on the doping, manifesting the intrinsic mechanism of the W layer in generating the spin Hall effect. This study shows promise of the magnetic-atom doped W/CoFeB/MgO/synthetic antiferromagnetic stacks to achieve high TMR and efficient type-Y SOT devices.