In this paper, micro gas chromatography columns were fabricated through the micro-electro-mechanical system (MEMS) technique. Two types of columns were designed, namely, open-tube and semi-packed columns. By comparing different structures, column efficiency was improved by embedding square posts in the channel to form a semi-packed column. The result showed that column efficiency of the semi-packed column reached 55 366 plates per m. This study was the first to report based on experimentation that MEMS-based columns can reach a plate number this high. The plate number was five times higher than the value previously reported. In addition, a 30 m-long Agilent HP-5 commercial capillary column was used to compare the results with findings obtained using a MEMS-based semi-packed column. The analytes were perfectly separated in both columns. The column efficiency of the HP-5 capillary column was 5490 plates per m, which was 10 times lower than that of the micro-fabricated, semi-packed column.