Periodic mesoporous organosilicas (PMOs) are one of the most promising candidates to be used as ultra-low-k dielectrics in microelectronic devices. In this paper, PMO thin films that combine an ultra-low-k value, a hydrophobic property and a high resistance against aggressive chemical conditions are presented. The films are synthesized via spin-coating of a 1,1,3,3,5,5-hexaethoxy-1,3,5-trisilacyclohexane, hydrochloric acid, water and ethanol mixture using polyoxyethylene (10) stearyl ether as a porogen template. The obtained highly porous films are hydrophobic, crack-free and an ultra-low k-value of 1.8 is achieved. Finally, the chemical resistance of these PMO films against alkaline solutions is investigated in detail and compared with the resistance of mesoporous silicas and PMOs synthesized with cetyl trimethylammonium chloride.