A new high performance RF LDMOS with vertical n+n-p-p+ drain structure

An improved radio-frequency (RF) lateral double-diffused metal-oxide-semiconductor (LDMOS) device based on Si-substrate process is proposed. The structure is characterized by a p⁺-buried-layer (PBL) buried under the drain in the p-substrate region. A vertical n⁺n^-p^-p⁺ diode formed at the drain side helps deplete the n-drift region and lengthen the lateral drift distance, thus effectively increasing the device breakdown voltage (BV_DS) with negligible disturbances to the on-resistance (R_on) and RF performance as the PBL is far away from the carrier channel. Both theoretical analysis and simulations of PBL effects are demonstrated. Compared with the conventional device, the proposed RF-LDMOS device increase by 19.8% and 12.2% in BV_DS and BV_DS*f_t, respectively.