dbcreator
Members of the dbcreator fixed server role can create databases, and can alter and restore their own databases.
See Also
Reference
Concepts
Permissions of Fixed Server Roles
Other Resources
sp_helpsrvrole (Transact-SQL)
sp_helpsrvrolemember (Transact-SQL)
sp_srvrolepermission (Transact-SQL)
Security Considerations for Databases and Database Applications