We present a static type discipline on an extension of lambda-calculus with threads and shared memory ensuring termination. This discipline is based on a type and effects system, and is a condition forced on regions. It generalizes and clarifies the stratification discipline previously proposed in the literature with the same objective, and is directly inspired by positive recursive types. The proof is carried out by translating the calculus with memory reference into an extension of lambda-calculus with a non-deterministic infinitary choice, whose strong normalization is in turn proved by a standard reducibility method.