U.S. activist hedge fund Third Point LLC expressed frustration Thursday over Sony Corp.'s decision to stick with the status quo and turn down a proposal to spin off its lucrative semiconductor business.

"It is difficult for us to imagine that a company of Sony's size and complexity could not find a single concrete action to improve its business and valuation," the New York-based fund, run by U.S. investor Daniel Loeb, wrote in a letter to investors. The fund has invested $1.5 billion in Sony.

In June, Third Point proposed that if Sony spun off the semiconductor business and executed on its long-term vision, the new entity could be worth $35 billion within five years.