Depends. If it is a detached ADU, and you have a two story main house, then the answer is likely YES with a maximum height of 24 feet! If the main house is one story, then the answer is no, but a loft space might be possible – depending on the maximum allowed height in your municipality (16 feet across the State).
How does it look in real life? Here is a photo taken during construction in Redwood City. This homeowner had decided to convert a detached garage into an ADU. The loft has a skylight and is waiting for the installation of the safety railing and ladder.
Add a cottage to your backyard 