Ferroelectric polarization, related to charge conduction, has shown some intriguing properties in ferroelectric tunnel junction as it has higher on/off ratio, lower power consumption and shorter process time. Conventional ferroelectrics have various problems when it is based on perovskite structure material, such as poor Si-compatibility, lead pollution and small energy bandgap. Recently, both ferroelectricity and anti-ferroelectricity have been reported in doped HfO₂ thin film (<30 nm). The ferroelectricity and anti-ferroelectricity HfO₂ thin films can be extremely thin with good Si-compatibility and large bandgap (>5 eV). Anti-ferroelectric/ferroelectric HfO₂ heterojunction can enhance fatigue property and non-linearity of single ferroelectric tunnel junction. The space charge can be induced due to the stress in ferroelectric layer or ferroelectric/metal interface in 90^° domain switching while anti-ferroelectric lowers the stress in the 180^° domain switching. The HfO₂ heterojunction can have non-linearity as it has higher resistance state under the threshold voltage for polarization switching. This structure with good fatigue property and non-linearity factor would contribute to the enhancement of ferroelectric tunnel junction memory device. This research was supported by the MOTIE (Ministry of Trade, Industry & Energy (#10080643) and KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device.