Semiconductor memory device and method for fabricating the same

Abstract

A low-leakage-current layer, made of BST in which the content of Ti deviates from its stoichiometric composition, is interposed between a high-dielectric-constant layer, made of BST with the stoichiometric composition, and an upper electrode. And a charge-storable dielectric film is made up of the high-dielectric-constant layer and the low-leakagecurrent layer. Such a BST film containing a larger number of Ti atoms than that defined by stoichiometry can suppress the leakage current to a larger degree. Also, if such a film is used, then the relative dielectric constant does not decrease so much as a BST film with the stoichiometric composition. Accordingly, the leakage current can be suppressed while minimizing the decrease in relative dielectric constant of the entire charge-storable dielectric film, which is a serial connection of capacitors, thus contributing to the downsizing of a semiconductor memory device. As a result, a semiconductor memory device, including a charge-storable dielectric film with decreased leakage current and enhanced charge storability, can be obtained.

Dependencies are inferred from the claim text.