Abstract: A new SOI LDMOS with folded silicon (FSOI-LDMOS) is proposed,in which the silicon substrate surface is trenched to form a folded shape from the channel to the drain electrode and the gate is extended to the drain.The majority-carrier accumulation layer is formed in the drift region because of the extended gate when the device is in the on state,and the concentration of drift region is higher than that in conventional SOI-LDMOS with the same breakdown voltage due to from the additional electric field modulation.The extra majority-carrier is introduced on the side-wall of the trench,which further reduces the on-resistance of the drift region.In addition the channel density is double due to trenching in the folded channel,which reduces the channel on-resistance.3D ISE simulation indicates that the ultra-low specific on-resistance is obtained with a breakdown voltage of less than 40V in FSOI-LDMOS.

Key words: folded silicon, SOI LDMOS, majority-carrier accumulation, breakdown voltage, specific on-resistance