We　present　a　new　metal-insulator-metal　(MIM)　heterowaveguide　to　enlarge　the　band　gap,　which　is　formed　by　alternately　stacking　two　kinds　of　metals,　modulating　the　MIM　waveguide　slit,　and　inserting　different　dielectric　materials　with　the　effective　refractive　index　periodically　modulated.　Based　on　this　structure,　we　adopt　two　different　methods　to　enlarge　the　band　gap:　changing　the　thickness　of　the　unit　layer　and　combining　two　MIM　structures.　Both　of　them　widen　the　band　gap　when　surface　plasmon　polaritons　propagate　through　the　structure.　This　metal　heterostructure　is　expected　to　have　applications　in　surface　plasmon　polaritons　(SPPs)　based　optical　devices,　such　as　filters,　waveguides,　especially　for　broad　band　gap　elements.　(c)　2008　Elsevier　B.V.　All　rights　reserved.