Hi S.,
My DS is now 14 and has always, thank God, been a champion sleeper. He always went to sleep in his bed, stayed in his bed and slept through when he was old enough, his entire life, spoiled me rotten on that front :-) .
Until he went through a phase at around 11. I'm trying to be diplomatic here....until one of his classmates introduced him to Slenderman. He was terrified, and who could blame him. He still stayed in his room for sleeping but it was at that age that we installed a nightlight both in the bathroom and in the corner of his room. I never really cottoned to night lights, as the human growth hormone is most effective if a person is sleeping in a dark room but this seemed to help him greatly during this phase. We also turned the bathroom exhaust fan on for him at night to help drown out or dampen any superfluous noises that may disturb him.
He has grown out of his fear and is old enough to get himself to bed at night, heck as early as I get up, there are nights when he tucks ME in before settling into read. So I discover what he's set up for himself when I awaken, sometimes the fan is on, sometimes not, sometimes the nightlights are burning and some nights they're not.
in terms of practical advice, my first suggestion would be to communicate as specifically as possible what his fears are and then try to specifically address them. Such as, is he afraid someone will come in through the window or a door? And then tell him the safeguards you have in place. Aside from our solutions above, I'll take it one step further and suggest, even though he's 11, maybe picking up a monitor so if/when he has a fright, all he has to do is call out for you and you can respond, reassure, comfort and help him allay the fear.
If you can take the unknown and turn it into a known, his fears should dissipate and he can outgrow this phase. 11 is hard at times and it sounds like he needs some unexpected but completely reasonable validation, comfort and reassurance.
It's healthiest for him to sleep in his bed for him to keep growing in all areas, body, mind and soul.
hoping this helps and finds you well. S.