For the current week, the overall ratings of four Semiconductor stocks are worse, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, OmniVision Technologies (NASDAQ:OVTI) falls to a D (“sell”), worse than last week’s grade of C (“hold”). OmniVision Technologies provides integrated single chip semiconductor imaging devices. In Portfolio Grader’s specific subcategories of Earnings Growth and Margin Growth, OVTI also gets F’s. As of Dec. 12, 2012, 14.8% of outstanding OmniVision Technologies shares were held short. The stock’s trailing PE Ratio is 48.40. For a full analysis of OVTI stock, visit Portfolio Grader.

Applied Materials (NASDAQ:AMAT) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Applied Materials manufactures and produces equipment, software, and other products for the flat-panel display, solar, and related industries. The stock receives F’s in Earnings Growth, Earnings Momentum, and Earnings Revisions. Margin Growth and Sales Growth also get F’s. The trailing PE Ratio for the stock is 122.80. To get an in-depth look at AMAT, get Portfolio Grader’s complete analysis of AMAT stock.

Cohu Inc. (NASDAQ:COHU) earns an F this week, falling from last week’s grade of D. Cohu develops, manufactures, markets, sells, and services test handling and burn-in related equipment and thermal sub-systems for the global semiconductor industry. The stock gets F’s in Earnings Growth, Earnings Revisions, and Equity. Margin Growth and Sales Growth also get F’s. For more information, get Portfolio Grader’s complete analysis of COHU stock.

This week, Ultra Clean Holdings’ (NASDAQ:UCTT) rating worsens to an F from the company’s D rating a week ago. Ultra Clean Holdings is a developer and supplier of critical subsystems, mainly for the semiconductor capital equipment industry. The stock gets F’s in Earnings Growth, Earnings Momentum, and Earnings Revisions. To get an in-depth look at UCTT, get Portfolio Grader’s complete analysis of UCTT stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.