How to identify SMD device marked LEFBV?
It's an IRLML0060TRPbF N-channel MOSFET

Maybe, anyway.

From the International Rectifier (now Infineon) datasheet, it matches your pinout:


  


And the markings seem very familiar, too:


  


L&#x332;E&#x332;F&#x305;B&#x305;V (your markings) would make the device:


IRLML0060 N-channel MOSFET
Produced in 2005 / 2015 week 32
Lot BV
Copper-wired
Halogen-free
Lead-free


The only thing that isn't 100% matching up is the overline on the B&#x305; (first letter of the lot code), I can't find any reference to that in the datasheet.