We introduce two nanoscale thickness dielectric layers on the top and bottom sides of a finite width and finite thickness metal microstrip and have calculated the fundamental symmetric plasmon-polariton mode of the 2D metal-dielectric layer waveguide. The dielectric nanolayers provide an additional degree of freedom to control the plasmon-polariton mode. When the dielectric constant of the nanolayers is smaller than that of the cladding dielectric, the travel range of the fundamental symmetric plasmon-polariton mode is extended with the trade-off of the mode confinement. The figure of merit of the mode increases as the travel range extends.