Measurements of the ion species generated in the neutral loop discharge (NLD) plasma of tetrafluoroethyl trifluoromethyl ether (HFE 227) demonstrateddd higher density of CF2+, CF3+ and C2F4+ ions than that of CF1+ ions. However, the etch selectivity of BPSG/resist was low in the HFE 227 plasma. Si (CH3) 3H (trimethylsilane) was added as a Si source to HFE 227 to enhance the selectivity and reduce the retardation of the resist sidewall. As a results, 0.15 μm in diameter holes with an aspect ratio of 15 were successfully fabricated. QMS and AMS measurements implied that the ultra high aspect feature was fabricated by the contribution of C2F4+ ions under lower density of radicals. Furthermore, the microloading-free etching was achieved at Vdc=-500 V for patterns till 0.15 μm holes and 50 nm line & 20 nm space patterns defined by electron beam lithography were also fabricated.