  Randall-Sundrum model, which has a scalar field, is used to investigate the
domain structure of the extra dimension and to obtain a possible solution of
the mass hierarchy problem. It is found that when the domain wall size is
comparable to that of domains, domains become unstable. To construct a reliable
theory, a region of physical parameter space, where domains are stable, is
identified. Analytic forms of field configurations are obtained by perturbative
expansions in term of a small parameter that is approximately equal to the
relative size of domain wall with respect to domains. By placing a single
3-brane in one of the domain, one can solve the mass hierarchy problem.
