This is an old revision of the document!
SPI serial SRAM chip. Looks like 4 metal layers and a fairly fine process geometry.
Definitely not one of Microchip's standard fan processes. CMP filler pattern is consistent with UMC 180 nm (pitch and dimensions of CMP filler and traces on both M4 and M3 match xc2c32a within 3%). Die logo etc also do not match the normal Microchip layout.