SanDisk and Toshiba have jointly developed the smallest 128Gbit NAND flash chip in the world by using a 3-bit multi-level cell design (TLC) and a 19nm process. The thing, just 170.6mm2 in area, is SanDisk's fifth generation of TLC technology. It uses something called All Bit-Line (ABL) programming and lots of technology tweaks …
If scaling the process down slows down speeds, and generally has a negative effect on flash performance, then why not just forget scaling the process down then? Need more bits? add another chip in the 3D stack of silicon that seems to be all the rage now.
I love how they also doubled the page size (again) to get twice the performance. Of course that increases write amplification (and thus reduces wear-life and performance) if you're not writing 16K blocks. Which nobody really does.
Oh well, it does say it's for tablets and smart phones, which nobody apparently expects to remain usable for longer than ~18 months, and flash write speed is waaaay less important than a large capacity number on the spec sheet (to marketing people, and probably most customers.)
Oh well, it's always good to see 'progress.' At least they came up with some new buzzwords to make this chip supposedly not as bad as it could have been.
Page size is not a problem on modern flash
All modern flash controllers write wherever the hell they want and maintain a mapping of the block number to its actual location on flash. When you write 16K of data, whether its 16K at once or a group of smaller pieces that total up to 16K, they'll get written in that one 16K block together and the flash translation layer (FTL) takes care of knowing where it is so you can read what you wrote.
I'm not sure about the granularity of the FTL, but given that hard drives used to be granular down to 512 bytes but are now granular to 4K, today 4K would be a reasonable minimum size. So on a 1TB drive the size of the table that mapped logical to physical block addresses would only be 1GB in size, a mere 0.1% of overhead. Perhaps a bit more since it would be smart to store a second copy of that data as its so vital!
Confused about density
Apparently this is the highest density flash memory available - 128Gbit in 170.6mm2. That's 0.75 Gbit/mm2.
In my phone I have a 32GB (256Gbit) microSD card. MicroSD cards are 15mmx11mm or 165mm2. If we assume that both sides of the card are used, and ignore any packaging, that would still be 128Gbit in 165mm2 or 0.78 GBit/mm2.
You're forgetting about stacking
Flash chips are typically stacked inside the package, as many as 8 chips on top of each other. Your MicroSD card probably has an 8x32Gbit stack inside it.