Quartz　is　widely　used　in　microelectromechanical　systems　(MEMS).　Especially,　MEMS　quartz　resonators　are　applied　to　sensors　and　serve　as　sensitive　elements.　The　capability　of　deep　etching　is　a　limitation　for　the　application.　Presented　in　this　paper　is　a　deep　and　high　accuracy　reactive　ion　etching　method　applied　to　a　quartz　resonator　etching　process　with　a　Cr　mask.　In　order　to　enhance　the　capability　of　deep　etching　and　machining　accuracy,　three　kinds　of　etching　gas　(C4F8/Ar,　SF6/Ar　and　SF6/C4F8/Ar),　bias　power,　inductively　coupled　plasma　(ICP)　power　and　chamber　pressure　were　studied　in　an　industrial　reactive　ion　etching　machine　(GDE　C200).　Results　indicated　that　the　SF6/C4F8/Ar　chemistry　gas　is　the　suitable　and　optimal　choice.　Experiment　results　indicate　that　Cr　(chromium)　mask　can　obtain　a　higher　selectivity　than　aluminum　and　titanium　mask.　A　＂sandwich＂　structure　composed　of　Al　layer-Cr　layer-Al　layer-Cr　layer　was　proposed.　The　Al　(aluminum)　film　can　play　the　role　of　releasing　stress　and　protecting　gold　electrodes,　which　can　enhance　the　thickness　of　metal　mask.　An　optimized　process　using　SF6/C4F8/Ar　plasmas　showed　the　quartz　etching　rate　of　450　nm/min.　Meanwhile,　a　microchannel　with　a　depth　of　75.4　µm　is　fabricated,　and　a　nearly　vertical　sidewall　profile,　smooth　surface　is　achieved.