New spin-on silicon hard mask (Si-HM) material containing Si-C structure in main chain was developed to meet EUV lithography performance, etch requirements and non-lithography patterning applications at sub 5 nm node. New Si-HM material can be used as an alternative to traditional polysiloxane Si-HM. It showed 2.5X high resistance for oxygen etching compared to polysiloxane Si-HM structure due to low electronegative gap and higher silicon content. It can be chemically modified with various functional units, and photoresist adhesion control would be expected to improve. We also observed sensitivity improvement from EUV lithography tri-layer patterning process including new Si-HM. Wet strip-ability with DHF and refractive index at 193 nm were changed significantly for this new Si-HM before and after UV irradiation under air. It also showed excellent gap-fill performance at narrow pattern dimensions on our patterned wafers.