* Offers $12.15/share, or 33 pct premium
* Verigy says offer not superior, but to talk to Advantest
* LTX says deal with Verigy remains in effect
* Verigy shrs up 36 pct; LTX shrs down 15 pct (Recasts; adds analysts' comments, details, updates shares)
By Himank Sharma
BANGALORE, Dec 6 (Reuters) - Semiconductor testing firm Verigy Ltd VRGY.O said it received a $728.8 million buyout offer from Tokyo-based Advantest Corp (6857.T) ATE.N, three weeks after the takeover target had agreed to acquire smaller rival LTX Credence LTXC.O in an all-stock deal.
Advantest's offer of $12.15 a share represents a premium of about 33 percent to Verigy's Friday's close on Nasdaq.
However, investors expecting a better deal bid up Verigy shares as much as 36 percent on Monday morning. They were trading at $12.40 midday, after touching a high of $12.42.
Cupertino, California-based Verigy said the latest offer is not superior to its pending transaction with LTX [ID:nSGE6AH0I2], but said it could lead to a superior transaction and that it will engage in discussions with Advantest.
DA Davidson analyst Thomas Diffely told Reuters that Advantest would come back with a higher bid, potentially breaking the LTX deal as the Japanese company is unlikely to buy the combined entity.
"We would argue that the combined company is worth more, but maybe Advantest does not want to pay that much money. Maybe it cannot afford to," Diffely said.
Separately, LTX-Credence said its $424.4 million merger agreement with Verigy remains in effect.
Advantest, which counts Intel Corp (INTC.O) as a customer for its memory testing equipment, was not immediately available for comment.
Stifel Nicolaus analyst Patrick Ho said if the Verigy deal goes through, Advantest would get access to the fast-growing system-on-chip (SoC) market, in addition to its memory testing customers.
"We believe an acquisition of Verigy would strongly position Advantest as the second leading SoC test supplier behind Teradyne," he said in a note.
Semiconductor makers rely on companies such as Verigy, Advantest and Teradyne Inc (TER.N) to test the efficiency and quality of their chips.
Analyst Diffely said although there is a bit of an overlap between the two companies' current product ranges, Advantest aims to achieve higher scale for its SoC product through the acquisition.
Shares of Advantest, with a market value of about $4.28 billion, were down 2 percent at $21.35 on the New York Stock Exchange.
LTX-Credence shares fell as much as 15 percent, making the stock one of the biggest losers on Nasdaq. They were down 12 percent at $7.40. (Reporting by Himank Sharma; Editing by Unnikrishnan Nair)