If you convert your @varDate local to a smalldatetime local before using it in the SELECT statement you can do a straight comparison of the local variable and the table column.

INSTEAD OF:

select * from table_name where dateDiff(d,@varDate,Created_Date) =0

TRY THIS:

DECLARE @sdtDate smalldatetime

SELECT @sdtDate = cast(@varDate AS smalldatetime)

SELECT * FROM table_name WHERE Created_Date = @sdtDate