No, serialisable doesn't force exclusive locks or table-level locks.
The isolation levels mostly change how read queries behave, not data modifications
You get a upd lock, on whatever resource SQL thinks is best (row, page or table) that's converted to exclusive to perform the update, that exclusive is then held until the end of the transaction. This is true in any isolation level.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability