Under the Residential Tenancies Act when a lease expires the tenants are allowed to remain on a month to month basis, they are not obligated to renew the lease for another 12 month term.
However, if both you and the tenant want to sign another lease, you must use the Ontario Residential Tenancy Agreement (Standard Form of Lease), which can be found at http://www.mah.gov.on.ca/Page18704.aspx