<p>Tamm plasmon polaritons (TPPs) supported by photonic-bandgap confinement provide a promising route toward compact and tunable terahertz (THz) photonic devices. This work proposes a spacer-assisted heterostructure composed of a thin highly doped indium antimonide (InSb) plasmonic layer coupled to a one-dimensional silicon/TPX distributed Bragg reflector (DBR). The results show that the structure supports a Tamm-type resonance inside the DBR stop band, producing a pronounced reflectance dip together with strong electric-field confinement and local enhancement. The resonance frequency is strongly affected by the carrier concentration of the InSb layer because the plasma frequency and Drude permittivity are controlled by doping. The effects of InSb thickness, DBR period number, and incident angle are also investigated, showing that the resonance position, linewidth and coupling strength can be systematically engineered in the THz range. The novelty of the proposed platform lies in using highly doped InSb as a semiconductor plasmonic layer for THz Tamm-state engineering, with realistic density-dependent effective mass and mobility included in the material model. The proposed structure is therefore a promising candidate for tunable THz filters, narrowband absorbers and refractive-index sensing platforms.</p>