Gap waveguide technology represents an emerging and interesting solution for the development of circuits and components operating in the millimeter-wave region and sub-millimeter-wave region. In these structures the energy is transmitted through the air gap existing between two parallel metal plates with HIS boundary conditions on laterals. These conditions are implemented by means of metallic posts homogenously distributed on both sides. This paper presents a new design based on Gap Waveguide concept using LTCC Technology in sub-millimeterwave. Compared to the SIW technology, the first interest is the non-presence of dielectric losses due to the propagation in air. Furthermore, it is shown that the technological constraints are less severe than for the conception of SIW waveguide (vias diameter and spacing). The concept is illustrated with a gapwaveguide around 150GHz.