IntroductionReRAM without selector is essentially desirable compared to other types such as 1D1R, and 1T1R because of high scalability and its simplicity in process. Thus, from that point of view, it is imperative to achieve good switching properties with high non-linearity in selector-less ReRAM. However, non-linearity, On/Off ratio, and operation voltage are complicatedly entangled in tradeoff relationship. In this study, we investigated the effect of non-stoichiometric TiN top electrode on switching behaviors and non-linearity properties of Ta 2 O 5 based ReRAM. As a result, thermodynamic approach has been made in explaining improvement of the amount of oxygen vacancies as well as the change in operation voltage with respect to Ti/N ratio has been scrutinized by measurement of the workfunction of the top electrodes.