An analytical model for a novel high voltage silicon-on-insulator device with composite-k(relative permittivity) dielectric buried layer(CK SOI) is proposed. In this structure, the composite-k buried layer is composed by alternating Si3N4 and low-k(k D 2.65) dielectric in the lateral direction. Due to the composite-k buried layer, the breakdown voltage(BV) is improved both by the vertical and lateral direction. Taking the modulation effect of accumulated interface holes into account, an analytical model is developed. In the blocking state, the proposed model revealed the mechanism of hole accumulation above the Si3N4 buried layer and investigated the modulation effect of accumulated holes on the two-dimensional(2-D) potential and electric field distributions. This analytical model is verified by the simulation results. Compared with the low-k dielectric buried layer SOI(LK SOI), simulation results show that the BV for CK SOI is enhanced by 21% and the specific on-resistance is reduced by 32%, respectively. An analytical model for a novel high voltage silicon-on-insulator device with composite-k (SOIC) dielectric buried layer (CK SOI) is proposed. In this structure, the composite-k buried layer is composed of alternating Si3N4 and low- Due to the composite-k buried layer, the breakdown voltage (BV) is improved both by the vertical and lateral directions. Taking the modulation effect of accumulated interface holes into account, an analytical model is developed. The proposed model revealed the mechanism of hole accumulation above the Si3N4 buried layer and investigated the modulation effect of accumulated holes on the two-dimensional (2-D) potential and electric field distributions. This analytical model Compared with the low-k dielectric buried layer SOI (LK SOI), simulation results show that the BV for CK SOI is enhanced by 21% and the specific on-resistance is reduced by 32%, respectively.