Semiconductor devices and semiconductor memory devices

Abstract

This invention provides a semiconductor device with excellent transistor characteristics. The semiconductor device of one embodiment includes: a first electrode; a second electrode; a first oxide semiconductor layer between the first electrode and the second electrode; a second oxide semiconductor layer spaced apart from the first oxide semiconductor layer in a second direction perpendicular to a first direction connecting the first electrode and the second electrode; a gate electrode surrounding the first oxide semiconductor layer and the second oxide semiconductor layer, extending in the second direction; and a gate insulating layer. The gate electrode includes a first portion and a second portion. The first portion faces the first oxide semiconductor layer in the second direction and is in contact with the gate insulating layer, having a first length in the first direction. The second portion has a second length in the second direction, extending from the first oxide semiconductor layer by a distance equal to half the distance between the first and second oxide semiconductor layers. The first length is longer than the second length.