Softbank Corp., Japan's third-largest mobile phone company, said it will acquire rival eAccess Ltd. in a stock transaction that values the smaller company's shares at an almost threefold premium.

Softbank will pay 16.74 of its shares for each share of eAccess, valuing the Tokyo-based company's stock at ¥52,000, President Masayoshi Son said at a press briefing on Monday.

Softbank will pay about ¥180 billion, Son said, adding that the merger will create a synergetic effect worth about ¥360 billion.

EAccess shares surged 26 percent to ¥19,000 in Tokyo trading, the most since its 2003 listing.

Son's wireless carrier will use eAccess' bandwidth to expand as increases in users of smartphones require more data capacity.

Softbank has surged 37 percent this year in Tokyo trading, outperforming bigger rivals NTT DoCoMo Inc. and KDDI Corp., and adding subscribers as the country's first carrier to offer Apple Inc.'s iPhone and iPad.

Son expressed his excitement about becoming the second-largest carrier with about 39 million subscribers when combining 4.2 million subscribers of Emobile, which is run by eAcess. The number of Softbank subscribers will surpass current No. 2 KDDI Corp's roughly 36 million.

Softbank decided on the acquisition to compete better with DoCoMo and KDDI, Son said, adding the carrier intends to accelerate the introduction of tethering service to Dec. 15. EAccess will be converted into a wholly owned unit and will be delisted Feb. 25.