Are Tenants sharing same database in Muti-tenancy architecture?

Are Tenants sharing same database in Muti-tenancy architecture?
if its same can we have separate database with restricted access for other Tenant?

All the tenants details and corresponding process details are stored in the same database only. Tenants concept comes into picture to restrict the access.
I think there is no way of creating a database per tenant. To restrict we create users only who wants to access the tenant.

Thanks