Abstract Selective isotropic cyclic dry etching of silicon oxide (SiO 2 ) was investigated using a three‐step cyclic process composed of hydrogen fluoride (HF) adsorption by NF 3 /H 2 remote plasma and reaction with NH 3 gas flow to form ammonium fluorosilicate ((NH 4 ) 2 SiF 6 ), and desorption by heating. The variation of the ratio of NF 3 :H 2 (2:1 to 1:3) and adsorption time (10–180 s) showed the highest etch selectivity of SiO 2 over Si 3 N 4 at 1:2 ratio of NF 3 :H 2 and with the adsorption time of 20 s. The etch selectivity higher than 40 was observed with 20 s of adsorption time with a 1:2 ratio of NF 3 :H 2 remote plasma and the total etch depth was linearly increased with the increase of cycles with the SiO 2 EPC of ~7.5 nm/cycle.