Semiconductor device with staircase gate stack and sidewall isolation structure

Abstract

Aspects of the disclosure provide a semiconductor device. The semiconductor device includes a memory stack of gate layers and insulating layers. The gate layers and the insulating layers are stacked alternatingly and are formed into stair steps in a staircase region. The semiconductor device includes a first landing pad on a first gate layer of a first stair step. The first gate layer is a top gate layer of the first stair step. The semiconductor device further includes a first sidewall isolation structure on a riser sidewall of a second gate layer of a second stair step. The second gate layer is a top gate layer of the second stair step and is stacked on the first gate layer in the memory stack. The first sidewall isolation structure isolates the second gate layer from the first landing pad.