LDMOS structure and method of making the same

摘要

In an LDMOS structure the N+ mask used for implanting the source region in self-alignment with the spacers formed on the edges of definition of the opening through the polysilicon gate layer (POLY), masks from the N+ implant an orthogonal strip across the full width of the poly opening, practically leaving in the masked area only the LDD N- source diffusion. This represents a discontinuity of the N+ source diffusion in the source region defined by the opening through the polysilicon layer, along with the W direction of the integrated LDMOS structure. Furthermore, P+ mask that is used for implanting the P+ dopant in the crossover area with the N+ mask, for realizing the body connection plug diffusion P+ and which eventually also increase the total dopant species concentration in the silicon region extending along the central axis of the source region in the width direction W of the integrated structure though without inventing the type of conductivity conferred to it by the higher N+ source implant, is centered about the central axis of the source region in the W direction. In this way, the body connection plug diffusion P+ is defined by way of the orthogonality of the two masks N+ and P+ (crossover area), without accounting for any overlay. The no longer critical character of the two masks and consequent elimination of overlays permits a significative reduction of the transversal width of the openings through the polysilicon gate layer and consequently a reduction of the pitch of integration.