This paper reports the development of a new class of high-performance microfabricated separation columns called high-density semi-packed columns (HDSPCs). These columns are realized by using a meter long and 145 μm-wide silicon microchannel design with embedded circular micropillars (15 μm diameters) and 5 μm post spacing (perpendicular to the gas flow). The HDSPCs are coated using our previously developed atomic layer deposition (ALD) based aluminium oxide and silane functionalized thin adsorbent film. Moreover, in this study we optimize both ALD deposition temperature (100 °C, 150 °C, 250 °C and 300 °C) and film thickness (10 nm, 20 nm and 30 nm) using different chromatographic parameters (plate number, peak-to-peak resolution, and separation factor). Additionally, the thermodynamic characteristics of these silane functionalized/ALD films are also studied using Van’t Hoff plots. These columns with optimized stationary phases are able to provide ≈8000 effective plates/meter and successfully separate a custom made hydrocarbon sample mixture with high peak-to-peak resolution.