KLA-Tencor (KLAC) shares are under pressure this morning following a pair of bearish Street research notes on the company which raise issues about the health of the company’s business with contract chipmaker Taiwan Semiconductor (TSM).

Oppenheimer’s Gary Hsueh this morning repeated his Underperform rating on the stock, asserting that “checks indicate new pressure on KLAC at TSMC, its most important foundry customer.” He says that TSMC has starting using inspection tools from Applied Materials on certain 45 nm lines, awarding AMAT “25%-33% of KLAC’s market share.” Hsueh also says that in reticle inspection, TSMC has postponed 1-2 orders for KLAC tools, “directly impacting” KLAC’s orders for the fiscal fourth quarter ended June. “We believe renewed competition at TSMC will add to KLAC’s share/margin issue,” he writes. “Worst case, if AMAT-driven pricing pressure is pervasive, we estimate 200-600 [basis points] of margin erosion for KLAC.”

Meanwhile, RBC Capital’s Mahesh Sanganeria this morning recommended a pair trade heading into June quarter earnings of long Novellus (NVLS) and short KLAC. “While consensus estimates for most semiconductor capital equipment companies may get minor downward revisions,” he writes, “we continue to see much larger risk to KLAC estimates.”

“Our checks show that some memory customers continue to face difficulty raising capital and are revising expansion plans resulting in another leg down in the September quarter,” Sanganeria writes. “We are also picking up some uncertainty in orders from TSMC (although small), probably due to a cut in wafers by Nvidia (NVDA).”

KLAC today is down $1.40, or 3.4%, to $39.25.