Design issues associated with integration of Horizontal Current Bipolar Transistor (HCBT) with 0.18 mu m bulk CMOS process are examined and the effects of fabrication parameters on transistor performance analyzed. HCBT is fabricated on a sidewall of a silicon hill defined by shallow trench isolation (STI). Height of the transistor is limited by the STI depth of 350 nm. Impact of vertical and horizontal dimensions on electrical performance of the transistor are analyzed by simulations with emphasis on extrinsic base design. Base current is reduced by high extrinsic base concentration and increased link-base length. Current gain is increased from 16 to 67 for transistor processed with the optimized extrinsic base profile. High-frequency performance is degraded by the collector charge sharing effect and can be improved by the larger separation between the extrinsic base and emitter, which is achieved with a small thickness of emitter polysilicon region. Misalignment tolerances of the extrinsic base implantation mask show no great impact on transistor's AC performance. (C) 2010 Elsevier Ltd. All rights reserved.