Semiconductor memory devices and methods for manufacturing semiconductor memory devices

Abstract

This invention relates to a semiconductor memory device and a method for manufacturing the semiconductor memory device. The semiconductor memory device of this embodiment includes: a first capacitor comprising a first electrode, a second electrode, and a first capacitor insulating film between the first and second electrodes; and a first transistor comprising a third electrode, a fourth electrode, a first oxide semiconductor layer between the third and fourth electrodes, and a first gate electrode; wherein the first electrode comprises a first portion, a second portion, and a third portion, the first chemical composition of the first portion differs from the third chemical composition of the third portion, the second chemical composition of the second portion differs from the third chemical composition of the third portion, the first portion is disposed between the third portion and the third electrode in a first direction, the second electrode comprises a fourth portion, and in a first cross-section perpendicular to the first direction and including the first and second electrodes, the second portion surrounds the fourth portion, and the fourth portion surrounds the first portion.

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