Intriguing polarization-mediated charge transport phenomena has driven extensive research on ferroelectric resistive memories, such as ferroelectric tunnel junction, switchable diode, and ferroelectric memristor. Recently, ferroelectric tunnel junction exhibited higher on/off ratio and lower power consumption. However, to realize high density memory devices that are compatible with cross-point stack structures, it requires high rectification and high non-linearity to prevent unwanted leakage current paths through neighboring cells (a well-known sneak path problem) in cross-point structures. In this study, we fabricated the ferroelectric tunnel junction memory device for application to highly integrated vertical memory devices. The charge conduction behavior with switching of ferroelectric polarization in BiFeO3 ultra-thin films based tunnel junctions were investigated. In addition, by introducing space charge layer in ferroelectric tunnel junctions, we demonstrated enhanced rectification and non-linearity in current-voltage characteristics for Pt/BiFeO3/Nb-SrTiO3 tunnel junctions. It was found that on /off ratio reached to maximum 104. Therefore, our ferroelectric tunnel junctions showing both high resistance ratio and nonlinearity factor offers a simple and promising building block of high density non-volatile memory. 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.