A new positive working photoresist which is applicable to the two-layer resist techniq using a current g-line stepper has been developed. This resist consists of a naphth, quinone diazide photoactive compound and a silicon containing novolak resin, which synthesized from m-trimethylsilylphenol, m-cresol, and formaldehyde by condensation r action according to the standard method. The 02 RIE durability of this resist gets great with increase of molar fraction of the silylphenol in the binder. The resist comprising resin prepared from the silylphenol alone by condensation with formaldehyde shows the highest 02 RIE durability,although resolution, sensitivity, and coating property are n sufficient. These properties are improved by incorporation of m-cresol moiety into t binder resin. Novo 1 ak prepared from a mixture of 30 mole % of m- creso 1 and 70 mole % of t silylphenol gives sufficient resolution, reasonable sensitivity and good coating proper leaving RIE durability at fairly high level. The molecular weight and the content of t sensitizer were optimized. The resist is completely compatible with current resist processings. The sensitivity good enough for the usual application and essentially no unexposed-film thickness loss w observed when it is developed with 2.38% tetramethylammonium hydroxide solution. Gam] value is fairly large and line and space as small as 0.6um can be resolved with go, profiles when it is exposed using a g-line stepper equipped with a lens of N.A.=0.35. This resist can be applied to the two-level resist process. MP-1400 was used as planarization layer and after curing at 200 C the present resist was applied on that as thin imaging resist. After exposure and development of the top layer, the pattern of 0. line and space was transferred to the bottom resist by 02 RIE with nearly vertical sil walls. The etch rates of top and bottom resist are shown to be 450 and 1360A/min, respectively.