­Japan's Softbank has announced a 36 percent fall in its second-quarter fiscal profits of 78.8 billion yen ($980 million) as the company invested in its network to boost capacity for smartphone users.

Softbank also had to take a one-off write down in the value of its stake in US games developer, Zynga which has seen its valuation plummet in recent months.

On a six-monthly basis, profits fell by 22% to 169.4 billion yen (US$2.13 billion) while sales rose 3.3 percent to 1.59 trillion yen.

The company is currently in the process of a US$20 billion purchase of a 70% stake in the USA based Sprint Nextel, having already agreed the takeover of smaller Japanese network, eAccess earlier this month.