Thin film SOI and SOS LDMOS structures with Linear Doping Profile and enlarged field plate

A new SOS (Silicon-On-Sapphire) LDMOS structure with Linear Doping Profile (LDP), or Variation on Lateral Doping (VLD) in the drift region, suitable for high voltage applications (> 600V) is proposed, analysed and compared with their SOI counterparts in this paper. An Extended Field Plate (EFP) including a step oxide is used to achieve a mirrored SOI-like structure which provides a vertical depletion of the drift region from the field oxide side. The electrical and thermal performances of the proposed structure have been obtained from technological and electro-thermal simulations. Although the subthreshold characteristics of the EFP-SOS LDMOS structure are similar than those of the EFP and FP-SOI counterparts, since the gate region parameters are identical, the blocking voltage and the conduction current capabilities are enhanced. In spite of the lower optimal N/sub d/ value used in EFP-SOS LDMOS transistors, their current capability is higher than that of the EFP-SOI ones due to the significant improvement of the generated heat extraction process.