A field effect transistor includes a plurality of trenches extending into a silicon layer. Each trench has upper sidewalls that fan out. Contact openings extend into the silicon layer between adjacent trenches such that each trench and an adjacent contact opening form a common upper sidewall portion....http://www.google.com/patents/US7595524?utm_source=gb-gplus-sharePatent US7595524 - Power device with trenches having wider upper portion than lower portion
