Non-volatile two transistor semiconductor memory cell and method for producing the same

Method for fabricating a nonvolatile two-transistor semiconductor memory cell, the method comprising:

• a) formation of a first insulation layer (3, 3′) for a selection transistor (AT) having a predetermined threshold voltage and a memory transistor (ST) having a predetermined threshold voltage on a semiconductor substrate (1), which has a doping of the first conduction type (p);
• b) formation of a semiconductor layer (4) at the surface of the first insulation layer (3, 3′);
• c) formation of a second insulation layer (5) at the surface of the electrically conductive semiconductor layer (4) at least in the region of the memory transistor (ST);
• d) formation of a further electrically conductive layer (6) at the surface of the second insulation layer (5) at least in the region of the memory transistor (ST);
• e) formation and patterning of a mask layer (7);
• f) formation of layer stacks in the region of the selection transistor (AT) and of the memory transistor (ST) using the patterned mask layer (7);
• and
• g) formation of source and drain regions (2) with a doping of the second conduction type (n) using the layer stack as mask, in which case in step a), the two threshold voltages in the selection and memory transistors (AT, ST) are raised by an increased doping of the semiconductor substrate (1), and
• in step b), for correction of the threshold raising in the selection transistor (AT), the semiconductor layer has a doping of the first conduction type (p) in a region of the selection transistor (AT) and a doping of the second conduction type (n), which doping is opposite to the first conduction type, in a region of the memory transistor (ST).