Taiwan Exchange curbs Formosa Sumco and Chroma after 40% share drop

The Taiwan Stock Exchange placed Formosa Sumco Technology and Chroma ATE under disposition trading curbs on Nov. 6, 2026, after their shares slumped more than 40% across six consecutive sessions.

The regulatory action transfers both semiconductor suppliers into manual order matching at two-minute intervals from Nov. 9 through Nov. 13, cooling turnover after abrupt institutional selling.

Formosa Sumco plunged 41.02% during the six-session window, registering a NT$99 ($3.10) closing price contraction, while Chroma ATE dropped 45.70% on a NT$550 ($17.20) spread, exchange records showed.

The combined market capitalization loss removed roughly NT$110 billion ($3.44 billion) from the two suppliers, shaking investor confidence across East Asia's upstream semiconductor materials and manufacturing equipment corridors.

Formosa Sumco operates 300-millimeter silicon wafer slicing and polishing lines in Yunlin, supplying roughly 15% of Taiwan's domestic wafer starts across memory and logic fabricators.

Chroma ATE supplies automated test systems and measurement equipment, drawing approximately 38% of its annual instrument revenue from advanced semiconductor packaging, power device validation and battery test programs.

Neither company filed regulatory disclosures detailing operational halts or material contract cancellations on the Market Observation Post System during the sell-off, corporate filings showed.

Taiwan's exchange authority flagged 67 equities for surveillance attention on Nov. 6 alone, reflecting broad liquidity shifts away from mid-cap technology suppliers toward primary foundry operators.

The disposition measure was executed under revised exchange directives adopted in August 2026, which shortened trading restriction intervals from 10 sessions down to five sessions.

Under the amended surveillance framework, bourses enforce a two-minute call auction matching cycle on designated equities, slowing order execution to dampen speculative turnover.

Brokers must also collect advance payment for buy consignments and demand pre-delivered share certificates from sellers when order sizes cross specific volume thresholds during the disposition window.

The sharp drop in wafer and test equipment values highlights diverging fortunes inside Taiwan's semiconductor ecosystem, where leading-edge wafer foundries remain heavily utilized while upstream component lines face order digestion.

Leading silicon foundries across Hsinchu and Tainan have prioritized memory-interconnect and wafer-level packaging capacity, but standard silicon wafer procurement has moderated following high distributor inventory levels.

Formosa Sumco faces softening spot pricing for 300-millimeter epitaxial wafers as contract clients exhaust existing warehouse buffer stocks accumulated during earlier production expansions.

Wafer manufacturing plants run at elevated energy and raw material overheads, which narrows operating margins when wafer volumes level off across trailing and specialty manufacturing nodes.

Test equipment builders face similar headwinds as device makers delay final evaluation sign-offs for second-tier production lines, stretching out delivery schedules for precision measurement racks.

Chroma ATE booked sustained order demand from high-performance computing power test benches, yet softer industrial power conversion equipment orders created near-term revenue friction.

Assembly and test contractors across Taichung and Kaohsiung have postponed discretionary equipment upgrades until first-quarter production schedules for consumer logic chips firm up.

Institutional sellers trimmed holdings across Asian packaging and testing vendors throughout the week, transferring capital into core foundry and high-bandwidth memory operations.

The surveillance notice published by the Taiwan Stock Exchange does not state whether officials will extend the disposition measure beyond the scheduled Nov. 13 market close.

The bourses have not published additional inspection findings regarding concentrated trading accounts or retail brokerage order spikes in either ticker during the six-day slide.

Contract terms between upstream wafer makers and foundry clients remain shielded by nondisclosure pacts, leaving the exact volume of deferred wafer intake unquantified in public filings.

Formosa Sumco and Chroma ATE are scheduled to exit the disposition regime when market trading opens on Nov. 16, restoring continuous electronic order matching unless volatility triggers further surveillance thresholds.