A multitier stack of memory cells having an aluminum oxide (AlOx) layer as a noble HiK layer to provide etch stop selectivity. Each tier of the stack includes a memory cell device. The circuit includes a source gate select polycrystalline (SGS poly) layer adjacent the multitier stack of memory cells, wherein the SGS poly layer is to provide a gate select signal for the memory cells of the multitier stack. The circuit also includes a conductive source layer to provide a source conductor for a channel for the tiers of the stack. The AlOx layer is disposed between the source layer and the SGS poly layer and provides both dry etch selectivity and wet etch selectivity for creating a channel to electrically couple the memory cells to the source layer.