ANALYSIS OF SI-GE SOURCE STRUCTURE IN 0.15 MU-M SOI MOSFETS USING 2-DIMENSIONAL DEVICE SIMULATION

We describe the technological potential of the bandgap engineering tec hnique involving a Si-Ge source structure in a fully-depleted SOI MOSF ET to suppress the Boating-body effect. The Si-Ge layer fabricated in the source region acts as an absorber for excess holes in the channel region. The detailed mechanism as well as the structure dependence in SOI MOSFETs with a gate length of 0.15 mu m have been studied using a two-dimensional device simulation. It has been found that the improvem ent in BVds is strongly dependent on the lateral position of the Si-Ge layer relative to the source-to-channel pn junction. It is further pr edicted that encroachment of the Si-Ge layer into the channel region a chieves the maximum BVds improvement. The BVds improvement is predicte d to reach 1.5 V if it proves possible to lower the energy barrier at the pn junction in the case where Delta E(g) = 0.2 eV.