LDMOS transistor
A lateral double-diffused MOS transistor (LDMOS) has a body zone and additional body regions assigned to the body zone, thereby producing a “deep body.” The deep body results in a quasi one-dimensional course of the potential lines, with the result that the dielectric strength is increased. The self-alignment between gate and channel is preserved, and parameter fluctuations are reduced.
1. An LDMOS transistor, comprising:
a semiconductor layer of a first conduction type;
a body zone of a second conduction type, opposite the first conduction type, formed in said semiconductor layer, said body zone having a lateral edge;
a highly doped source zone of the first conduction type formed in said body zone;
a highly doped drain terminal zone of the first conduction type formed in said semiconductor layer at a distance from said body zone;
a gate, said body zone being self-aligned with respect to said gate;
at least one additional body region disposed below said body zone in said semiconductor layer and projecting beyond said lateral edge of said body zone at least in a direction towards said drain terminal zone.
2. The LDMOS transistor according to claim 1 , wherein said at least one additional body region is one of a plurality of additional body regions extending farther toward said drain terminal zone with an increasing depth in said semiconductor layer.
3. The LDMOS transistor according to claim 1 , wherein said additional body region is provided under a RESURF zone of the first conduction type.
4. The LDMOS transistor according to claim 1 , wherein said semiconductor layer is disposed over a buried layer on a semiconductor substrate.
5. The LDMOS transistor according to claim 4 , wherein said buried layer has the first conduction type.
6. The LDMOS transistor according to claim 4 , wherein said buried layer has the second conduction type.
7. The LDMOS transistor according to claim 1 , which comprises a thick insulating layer, and wherein said gate extends over said thick insulating layer.
8. The LDMOS transistor according to claim 1 , wherein the first conduction type is an n conduction type.
9. The LDMOS transistor according to claim 1 , which comprises a buffer zone of the first conduction type, and wherein said drain terminal zone is embedded in said buffer zone.
10. The LDMOS transistor according to claim 1 , which further comprises a buried layer, and wherein said additional body regions are disposed at a distance from said buried layer.
11. In a method for fabricating the LDMOS transistor according to claim 1 , which comprises: carrying out at least one implantation to form the at least one additional body region prior to depositing a polycrystalline silicon layer for forming a gate of the LDMOS transistor according to claim 1 .
12. The method according to claim 11 for fabricating a transistor with the additional body region provided under a RESURF zone of the first conduction type, which comprises counterdoping a doping of the RESURF zone in the source region, for forming the body zone.
13. In a method for fabricating the LDMOS transistor according to claim 7 , which comprises: carrying out at least one implantation to form the at least one additional body region prior to forming the thick insulating layer on a surface of the semiconductor layer of the LDMOS transistor according to claim 7 .
14. The method according to claim 13 for fabricating a transistor with the additional body region provided under a RESURF zone of the first conduction type, which comprises counterdoping a doping of the RESURF zone in the source region, for forming the body zone.