Three-dimensional memory string array of thin-film ferroelectric transistors formed with an oxide semiconductor channel in a channel last process

Abstract

A memory structure includes storage transistors organized as horizontal NOR memory strings where the storage transistors are thin-film ferroelectric field-effect transistors (FeFETs) having a ferroelectric gate dielectric layer formed adjacent an oxide semiconductor channel region. The ferroelectric storage transistors thus formed are junctionless transistors having no p/n junction in the channel. In some embodiments, the ferroelectric storage transistors in each NOR memory string share a common source line and a common bit line that are formed on a first side of the channel region, away from the ferroelectric gate dielectric layer, and in electrical contact with the oxide semiconductor channel region. The ferroelectric storage transistors in a NOR memory string are controlled by individual control gate electrodes that are formed adjacent the ferroelectric gate dielectric layer on a second side, opposite the first side, of the channel region.