Infineon Technologies Ag

Yoichi Otani

Andreas Rusch

Thomas B&ouml;hm

Armin Kohlhase

Ulrich Zimmermann

Manfred Hain

Volker Weinrich

Till Schl&ouml;sser

Steffen Rothenhäusser

Alexander Tr&uuml;by

A method for fabricating a semiconductor memory device is described. An insulating layer is disposed on a semiconductor substrate. A matrix of semiconductor memory elements is disposed in the substrate. The semiconductor memory elements include a plurality of contact holes formed in the insulating layer. One contact hole is formed in the insulating layer for each of the semiconductor memory elements. A bit definition region is disposed in the semiconductor substrate underneath each of the contact holes. A contact plug is disposed in each of the contact holes and is in electrical contact with the bit definition region. The bit definition region is configured such that a contact resistance between the semiconductor substrate and the contact plug defines a bit to be stored in the semiconductor memory elements, An evaluation circuit is connected to and evaluates the contact resistance of the semiconductor memory elements.

Method of making a semiconductor memory device

The memory cell configuration has a large number of memory cells provided in a semiconductor substrate and having bit-line trenches which extend in parallel in the longitudinal direction in the main face of the semiconductor substrate, at the bottoms of which in each case a first conductive region is provided, at the peaks of which in each case a second conductive region of the same conduction type as the first conductive region is provided, and in the walls of which in each case an intermediately located channel region is 0 provided; and having word lines which extend in the transverse direction along the main face of the semiconductor substrate, through specific bit-line trenches, to activate transistors provided there. An additional dopant is introduced into the trench walls of the bit-line trenches which are located between the word lines, in order to increase the corresponding transistor turn-on voltage there to suppress leakage currents.

Memory cell configuration and corresponding production process

The memory cell configuration has a multiplicity of preferably ferroelectric memory cells in a semiconductor substrate. Mutually parallel bit line trenches run in the longitudinal direction in the main surface of the semiconductor substrate. Bit lines are disposed in the bottoms of the trenches. Source/drain regions are formed in the crowns of the trenches. Channel regions are provided in the walls of the trenches. The channel region on a wall in each case is configured such that a drivable selection transistor of the relevant memory cell is formed there, while the channel region on the other wall is configured such that the transistor located there is closed. Insulated word lines for driving the selection transistors run in the transverse direction along the main surface of the semiconductor substrate through the bit line trenches. Insulation trenches for insulating the source/drain regions in the longitudinal direction of neighboring memory cells run in the transverse direction in the main surface of the semiconductor substrate. A respective, preferably ferroelectric, capacitor is connected to the source/drain region of the respective memory cell and is arranged above the word lines.

Memory cell configuration and corresponding fabrication method

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Weixdorf, Germany

Yoichi Otani