Design of SOI MOSFETs for Analog/RF Circuits

Abstract

In this paper, the concept of integration of a high voltage trench MOSFET (HVT MOSFET) and low voltage trench MOSFET (LVT MOSFET) is proposed. Insulator (Dielectric) isolation technique is used for the implementation of HVT and LVT MOSFETs on Silicon-on-Insulator (SOI) layer side by side. The HVT MOSFET consists of two gates which are placed in separate trenches in the drift region. The proposed structure minimizes ON-resistance (R_on) along with increased breakdown voltage (V_br) due to reduced electric field, creation of dual channels, and folding of drift region in vertical direction. In HVT MOSFET, the drain current (I_D) increases leading to enhanced trans conductance (g_m) by simultaneous conduction of channels which improves the cut-off frequency (f_t) and maximum oscillation frequency (f_max). On the other side, LVT MOSFET consists of a gate placed within a SiO₂ trench to create two channels on either side of gate. The parallel conduction of two channels provides enhancement in I_D, g_m, f_max and f_t. The performance analysis of HVT MOSFET and LVT MOSFET is carried out using 2D simulation in the device simulator (ATLAS).