Event
ECE Colloquium Series - Steven Koester, University of Notre Dame
Friday, March 27, 2026
3:30 p.m.-4:30 p.m.
Jeong H. Kim Engineering Building, Room 1110
Darcy Long
301 405 3114
dlong123@umd.edu
Speaker: Dr. Steven Koester, Department of Electrical Engineering, University of Notre Dame
Talk Title: Challenges and Opportunities for TMD MOSFETs to Extend Moore’s Law Scaling into the Monolithic 3D Era
Abstract: As conventional silicon CMOS approaches fundamental electrostatic and power-density limits, continued scaling requires new materials and integration approaches. Transition metal dichalcogenides (TMDs), such as WS 2 , MoS 2 and WSe 2 , have emerged as leading candidates for channel materials in next-
generation MOSFETs due to their extremely thin nature and excellent transport properties. These attributes make TMD devices particularly attractive for aggressive scaling in stacked nanosheet geometries and 3D-integrated devices in the back-end-of-the-line (BEOL). However, many materials and processing challenges remain. In this talk, I will provide an overview of the opportunities and challenges associated with using TMDs for ultimate-scaled MOSFETs and monolithic 3D integration. I will first describe our work addressing the contact problem with TMD MOSFETs. We demonstrated extremely-low-resistance n-type contacts to WS 2 using bismuth (Bi), but also showed that the contacts were still vulnerable to electrostatic gating. More recently, we studied ultra-low-resistance p-type contacts using Nb-doped WS 2 (Nb:WS 2 ) thin films grown by plasma-enhanced ALD (PEALD). Contact resistance values as low as 300 Ω–μm were achieved, with specific contact resistivity as low as 11 nΩ-cm 2 . We have also fabricated short-channel WSe 2 p-MOSFETs using Nb:WS 2 contacts to WSe 2 and these devices showed promising performance with drive currents exceeding 100 mA/mm. More recently, we have investigated potential applications of TMDs for BEOL-compatible 3DICs. We demonstrated WS 2 p-MOSFETs with channel thickness as low as 1.4-nm grown by PEALD and showed that PEALD Nb:WS 2 is also a promising material for passive elements, such as thin-film resistors. Finally, I will describe the wide range of future opportunities for TMDs in monolithic 3DICs, including memristors, 3D DRAM and NAND flash, interconnects, and many others.
Bio: Dr. Koester is the Frank M. Freimann Professor of Microelectronics, and Director of Notre Dame Nanoscience and Technology (NDnano) at the University of Notre Dame. He received B.S.E.E. and M.S.E.E. degrees from Notre Dame in 1989 and 1991, and the Ph.D. in 1995 from the University of California, Santa Barbara. From 1997 to 2010, he was a research staff member at the IBM T. J. Watson Research Center and performed research on a wide variety of electronic and optoelectronic devices, with an emphasis on the Si/SiGe material system. From 2006 to 2010 he served as manager of Exploratory Technology at IBM Research where his team investigated novel devices and advanced CMOS integration concepts. From 2010-2025, Dr. Koester was a Professor of Electrical & Computer Engineering at the University of Minnesota, where his research focused on novel electronic, photonic, spintronic, and sensing device concepts. Dr. Koester has authored or co-authored over 300 technical publications and conference presentations, 7 volumes, 4 book chapters, and holds 82 United States patents. He is a Fellow of the IEEE, Optica, and the National Academy of Inventors.
