Abstract: An erasable programmable read only memory (EPROM) cell having a floating gate and a control gate where the floating gate and the control gate are deliberately offset or asymmetrical from the source/drain and drain/source regions in the substrate. During programming, the source region is the one spaced apart from the gates while the drain region is aligned thereto. This orientation produces high gate currents to provide faster programming. During a read operation the aligned region now becomes the source and the spaced apart region becomes the drain to provide high drain currents for fast access. The asymmetrical EPROM cells of the present invention may be readily made using conventional spacer technology.

Abstract: Implementing modified souce/drain implants in a non-volatile memory process while leaving the source/drain regions in the memory cells of the device unmodified and adding no critical mask steps. Methods for implementing both low dose drain and graded source/drain modifications in a double poly non-volatile memory process include the possibility of leaving the spacers used to modify the peripheral source/drain regions in place in the array portion of the device. Alternate methods include the possibility of removing the spacers in the array portion without the addition of critical mask steps and of keeping the spacers out of the array portion entirely.

Abstract: A process for forming lightly doped drains in a CMOS circuit utilizing two photoresist masks is disclosed. After gates for N-channel and P-channel transistors have been formed, an N-implant is effected. A first photoresist mask is used as a source/drain implant is made for the P-channel transistor. Sidewall spacers are formed for the gates of both transistors. A second photoresist mask is used as a source/drain implant is made for the N-channel transistor. The resulting CMOS circuit has an N-channel transistor with a lightly doped drain and a P-channel transistor without a lightly doped drain.