Actually this is a IO bottleneck and not memory. Memory shows up as RESOURCE_SEMEPHORE.
This is a wait for the IO channel to read a Page from the IO Channel. The Latch is a shared memory key for a specific page of IO (disk) memory. If you have your process ID in the latch memory location, you own the page of IO. If some other process has it's ID, you wait. This is how SQL controls access to physical IO of the system.
This is NOT the same as a page lock as this would show up as blocking. This WAIT type shows up simply because the IO activity of the computer is busy.
Faster IO would be better or more disk spindles or faster disk channels (not to exclude a faster/wider bus).